Thin thermally and chemically strengthened glass-based articles

ABSTRACT

Embodiments of thermally and chemically strengthened glass-based articles are disclosed. In one or more embodiments, the glass-based articles may include a first surface and a second surface opposing the first surface defining a thickness (t), a first CS region comprising a concentration of a metal oxide that is both non-zero and varies along a portion of the thickness, and a second CS region being substantially free of the metal oxide of the first CS region, the second CS region extending from the first surface to a depth of compression of about 0.17●t or greater. In one or more embodiments, the first surface is flat to 100 μm total indicator run-out (TIR) along any 50 mm or less profile of the first surface. Methods of strengthening glass sheets are also disclosed, along with consumer electronic products, laminates and vehicles including the same are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application and claims the benefit ofpriority under 35 U.S.C. § 120 of U.S. application Ser. No. 15/404,823filed on Jan. 12, 2017, which in turn, claims the benefit of priorityunder 35 U.S.C. § 119 of U.S. Provisional Application Ser. No.62/303,608 filed on Mar. 4, 2016, U.S. Provisional Application Ser. No.62/288,827 filed on Jan. 29, 2016 and U.S. Provisional Application Ser.No. 62/277,579 filed on Jan. 12, 2016, the contents of each of which arerelied upon and incorporated herein by reference in their entireties.

BACKGROUND

The disclosure relates to improved and thin thermally and chemicallystrengthened glass articles and improved methods for strengthening glasssubstrates, and relates more particularly to thin glass articlessimultaneously exhibiting a deep depth of compression and high surfacecompressive stress.

Thermally strengthened glass articles are strengthened by heating aglass substrate to an elevated temperature above the glass transitiontemperature of the glass, and cooling the surfaces of the substraterapidly (“quenching”), while the inner regions of the substrate,insulated by the thickness and fairly low thermal conductivity of theglass, are cooled at a slower rate. This differential cooling produces aresidual compressive stress (CS) in the surface regions of the thermallystrengthened glass article, balanced by a residual tensile stress in thecentral region thereof.

Thermal strengthening is distinguished from chemical strengtheningprocesses, in which surface compressive stresses are generated bychanging the chemical composition of the glass in regions near thesurface by a process such as ion diffusion. In some ion diffusion basedprocesses, exterior portions of the resulting glass article may bestrengthened by exchanging larger ions for smaller ions near the surfaceto impart a CS (also called negative tensile stress) on or near thesurface.

Thermal strengthening and chemical strengthening processes aredistinguished from mechanical glass strengthening processes in whichexterior portions of the glass article are strengthened or arranged bycombining two types of glass. In such processes, layers of glasscompositions that have differing coefficients of thermal expansion arecombined or laminated together while hot. For example, by sandwichingmolten glass with a higher coefficient of thermal expansion (CTE)between layers of molten glass with a lower CTE, positive tension in theinterior glass compresses the outer layers when the glasses cool, againforming CS on the surface to balance the positive tensile stress.

Strengthened glass articles have advantages relative to unstrengthenedglass articles. The surface compressive stress of the strengthened glassarticles provides greater resistance to fracture than unstrengthenedglass. The increase in strength generally is proportional to the amountof surface compression. If a glass article possesses a sufficient levelof strengthening, relative to its thickness, then when and if the sheetis broken, it will divide into small fragments with dull edges ratherthan into large or elongated fragments with sharp edges. Glass thatbreaks into sufficiently small fragments, or “dices,” as defined byvarious established standards, may be known as safety glass, and isoften referred to as “fully tempered” glass, or sometimes simply“tempered” glass.

With at least thermally strengthened glass articles, because the degreeof strengthening depends on the temperature difference between thesurface and center of the glass sheet, thinner glasses require highercooling rates to achieve a given stress. Also, thinner glass generallyrequires higher final values of surface CS and central tensile stressesor central tension (CT) to achieve dicing into small particles uponbreaking. Accordingly, achieving desirable dicing behavior in thin glassarticles (i.e., articles with a thickness of around 3 mm or less) usingknown thermal strengthening processes alone or in combination with otherstrengthening process has been exceedingly challenging if notimpossible. Moreover, such thin glass articles often do not exhibit highsurface compressive stresses, which prevent flaw or crack nucleationand/or growth. Accordingly, there is a need for thin glass articlesexhibit deep depths of compression while also exhibiting high surfacecompressive stresses.

SUMMARY

A first aspect of this disclosure pertains to thermally strengthened andchemically strengthened glass-based articles. In this disclosureglass-based substrates are generally unstrengthened and glass-basedarticles generally refer to glass-based substrates that have beenstrengthened (by, for example, thermal strengthening and/or chemicalstrengthening).

In one or more embodiments, the glass-based article includes a firstsurface and a second surface opposing the first surface defining athickness (t). The first and second opposing surfaces may includeopposing major surfaces of the article. In some embodiments, thethickness of the glass-based article t is less than about 2 mm or lessthan about 1.2 mm. In some instances, the glass-based article comprisesa glass sheet having a length, expressed in millimeters, of l, and awidth, expressed in millimeters, of w, wherein the thickness t is lessthan l and less than w, and l and w are each at least 10 mm. In someinstances, either one or both l and w are at least 40 mm. The ratio l/tand the ratio w/t each are equal to 10/1 or greater, in accordance withone or more embodiments.

In one or more embodiments, the glass-based article includes a first CSregion comprising a concentration of a metal oxide that is both non-zeroand varies along a portion of the thickness, and a second CS region. Inone or more embodiments, the metal oxide having a varying concentrationin the first CS region generates a stress along the specified thicknessrange. In some embodiments, this metal oxide may have the largest ionicdiameter of all of the total metal oxides in the glass-based article. Inother words, the metal oxide having a varying concentration may be themetal oxide that is ion exchanged into the glass-based article. In oneor more embodiments, the second CS region may include a constant metaloxide concentration region or, in other words, is substantially free ofthe metal oxide that is non-zero and varies along the first CS region.As used herein, the phrase “substantially free of the metal oxide thatis non-zero and varies along the first CS region” means that less thanabout 0.1 mol % of the metal oxide is present in the second CS region.In some embodiments, the composition of the second CS is substantiallyconstant throughout the thickness of the second CS region. In one ormore embodiments, the second CS region extends from the first CS regionto a depth of compression (DOC), wherein the DOC is about 0.17●t orgreater. In some embodiments, the concentration of the metal oxide isboth non-zero and varies along the portion of the thickness from thefirst surface to a depth in the range from greater than about 0●t toless than about 0.17●t or in the range from greater than about 0.01●t toabout 0.1●t.

In one or more embodiments, the glass-based article includes a thermallystrengthened region extending from the first surface to a DOC and achemically strengthened region extending from the first surface to adepth of layer (DOL). As used herein, the term “thermally strengthenedregion” includes a region exhibiting a compressive stress primarily dueto a thermal strengthening process. Such thermally strengthened regionsmay also exhibit some stress due to chemical strengthening (e.g., thepenetration of metal ions into deeper regions of the glass-based articlewhich may contribute some stress, but such stress is not the primarycontribution to the total compressive stress in the region). As usedherein, the term “chemically strengthened region” includes a regionexhibiting a compressive stress generated at least in part to a chemicalstrengthening process. Such chemically strengthened regions may alsoexhibit some stress due to thermal strengthening process. The DOC ofsome embodiments is greater than DOL and DOC is greater than or equal toabout 0.17●t.

As used herein, DOC refers to the depth at which the stress within theglass-based article changes from compressive to tensile stress. DOLrefers to the stress generated as a result of chemical strengthening. Atthe DOC, the stress crosses from a compressive stress to a tensilestress and thus exhibits a stress value of zero.

According to the convention normally used in the art, compression isexpressed as a negative (<0) stress and tension is expressed as apositive (>0) stress; however, throughout this description, CS isexpressed as a positive or absolute value—i.e., as recited herein,CS=|CS|, and CT is also expressed as an absolute value, i.e., as recitedherein, CT=|CT|.

In some embodiments, the surface CS of the glass-based article may beabout 400 MPa or greater, or about 600 MPa or greater. In one or moreembodiments, the surface CS may be about 1 GPa or greater. In someembodiments, the glass-based article exhibits a maximum CT of about 75MPa or greater, or even 80 MPa or greater. In one or more embodiments,the glass-based article includes a stored tensile energy of about 6 J/m²or greater or about 10 J/m² or greater.

The glass-based article of one or more embodiments may exhibit a CSvalue at a depth equal to the DOL of about 150 MPa or greater. In one ormore specific embodiments, the DOL at which the CS is about 150 MPa orgreater, may be about 10 micrometers or greater (or about 0.01●t orgreater).

In one or more embodiments, the glass-based article includes a firstsurface that is flat to 100 μm total indicator run-out (TIR) along any50 mm or less profile of a first surface. In one or more embodiments,the first surface has a roughness in the range of from 0.2 to 1.5 nm Raover an area of 10×10 μm.

In some embodiments, the glass-based article comprises a glass having asoftening temperature, expressed in units of ° C., of T_(soft) and anannealing temperature, expressed in units of ° C., of T_(anneal), and asurface fictive temperature measured on the first surface represented byTfs, when expressed in units of ° C. and a non-dimensional surfacefictive temperature parameter θs given by(Tfs−T_(anneal))/(T_(soft)−T_(anneal)), wherein the parameter θs is inthe range of from 0.20 to 0.9.

In some embodiments, the Tfs measured on the first surface is at least50° C. above a glass transition temperature of the glass. In one or moreembodiments, the Tfs measured on the first surface is at least 75° C.above a glass transition temperature of the glass.

The glass-based articles described herein may include a compositionincluding P₂O₅, Li₂O, B₂O₃ or various combinations of P₂O₅, Li₂O andB₂O₃.

A second aspect of this disclosure pertains to a method forstrengthening a glass-based sheet. In one or more embodiments, themethod includes cooling a glass sheet having a transition temperature,from a temperature greater than the transition temperature to atemperature less than the transition temperature by transferring thermalenergy from the glass sheet to a heat sink by conduction across a gapthat is free of solid or liquid matter to thermally strengthen the glasssheet, and then chemically strengthening the thermally strengthenedglass sheet. In one or more embodiments, the method includestransferring thermal energy from the glass sheet to a heat sink byconduction across the gap such that more than 20%, more than 30%, morethan 40% or more than 50% of the thermal energy leaving the glass sheetcrosses the gap and is received by the heat sink.

In one or more embodiments, the method includes supporting at least aportion of a glass-based sheet on a first surface thereof, at least inpart, by a flow or a pressure of a gas delivered to a gap between thefirst surface and a first heat sink, wherein the sheet comprises a glasshaving a transition temperature and the sheet is at a temperaturegreater than the transition temperature of the glass, cooling theglass-based sheet, by thermal conduction more than by convection, fromthe first surface of the sheet through the gas to a heat sink to providea thermally strengthened glass-based sheet, and chemically strengtheningthe thermally strengthened glass-based sheet.

In one or more embodiments, the thermally strengthened glass-based sheetis chemically strengthened without removing any portion of the thermallystrengthened glass-based sheet. In some instances, the thermallystrengthened glass-based sheet is chemically strengthened withoutremoving 3% or more of the thickness of the thermally strengthenedglass-based sheet. Cooling the glass-based sheet may include cooling ata rate of about −270° C./second or greater.

In one or more embodiments, chemically strengthening the thermallystrengthened glass-based sheet includes generating a chemicallystrengthened region that extends from a first surface of the glass-basedlayer to a DOL that is greater than or equal to about 10 micrometers (orgreater than about 0.01●t). In some embodiments, chemicallystrengthening the thermally strengthened glass-based sheet comprisesimmersing the thermally strengthened glass-based sheet in a molten saltbath comprising any one or more of KNO₃, NaNO₃, and LiNO₃. In someembodiments, the molten salt bath includes a combination of KNO₃ andNaNO₃ and has a temperature in the range from about 380° C. to about430° C.

A third aspect of this disclosure pertains to a consumer electronicproduct. In one or more embodiments, the consumer electronic product mayinclude a housing having a front surface, a back surface and sidesurfaces, electrical components disposed at least partially inside orinternal to the housing, and a cover article provided at or over thefront surface of the housing. In one or more embodiments, the electricalcomponents include at least a controller, a memory, and a displaydisposed at or adjacent the front surface of the housing. In someembodiments, the cover article is disposed over the display and is athermally and chemically strengthened glass-based article, as describedherein. In one or more embodiments, the consumer electronic product is amobile phone, portable media player, notebook computer or tabletcomputer.

A fourth aspect of this disclosure pertains to a laminate comprising afirst glass-based substrate, a second glass-based substrate and aninterlayer disposed between the first glass-based substrate and thesecond glass-based substrate. In one or more embodiments, either one orboth the first and second glass-based substrate is a thermally andchemically strengthened glass article as described herein.

In one or more embodiments of the laminate, one of the first glass-basedsubstrate and the second glass-based substrate is cold-formed.

In one or more embodiments of the laminate, the first glass-basedsubstrate is complexly-curved and has at least one concave surfaceproviding a first surface of the laminate and at least one convexsurface to provide a second surface of the laminate opposite the firstsurface. In one or more embodiments, the second glass-based substrate ofthe laminate is complexly-curved and has at least one concave surface toprovide a third surface of the laminate and at least one convex surfaceto provide a fourth surface of the laminate opposite the third surface,wherein the third and fourth surfaces respectively have CS values suchthat the fourth surface has a CS value that is greater than the CS valueof the third surface. In some embodiments, the fourth surface of thelaminate has a greater CS than the fourth surface has in a flat stateand the laminate is free from optical distortions when viewed with thenaked eye.

In one or more embodiments, one of the first glass-based substrate orthe second glass-based substrate of the laminate has a thickness in therange of about 0.2 mm to about 0.7 mm.

In one or more embodiments of the laminate, a peripheral portion of thesecond glass-based substrate exerts a compressive force against theinterlayer, and a center portion of the second glass-based substrateexerts a tensile force against the interlayer. In one or moreembodiments, the second glass-based substrate conforms to the firstglass-based substrate to provide a substantially uniform distancebetween the convex surface of the second glass-based substrate and theconcave surface of the first glass-based substrate, which is filled bythe intervening interlayer.

A fifth aspect of this disclosure pertains to a vehicle comprising anopening; and a laminate (as described herein) disposed in the opening.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments as described herein, including the detailed descriptionwhich follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understanding the natureand character of the claims. The accompanying drawings are included toprovide a further understanding, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiment(s), and together with the description serve to explainprinciples and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of blower power required for known full temperingprocesses as a function of glass article thickness;

FIG. 2 is a graph of blower power required for “full tempering” as afunction of glass article thickness for an old and known process ormachine O and a newer and known process or machine N;

FIG. 3 is a graph of the curve O and the curve N of FIG. 2 scaled tomatch and superimposed upon the graph of FIG. 1;

FIG. 4 is a cross-sectional view across a thickness of a known,chemically strengthened glass-based article;

FIG. 5 is a graph illustrating a stress profile as a function ofglass-based article thickness according to one or more embodiments ofthis disclosure;

FIG. 6 is a perspective view of a thermally and chemically strengthenedglass-based article according to an exemplary embodiment;

FIG. 7 is a diagrammatic partial cross-section of a thermally andchemically strengthened glass-based article of FIG. 6 according anexemplary embodiment;

FIG. 8 is a plot of the non-dimensional surface fictive temperatureparameter θs for fictive temperatures obtained by one or moreembodiments;

FIG. 9 is a plot of surface CS values calculated by simulation fordiffering glass compositions, plotted against a proposed temperabilityparameter Ψ for the various compositions shown;

FIG. 10 is a graph of parameter P₁ as a function of heat transfercoefficient h;

FIG. 11 is a graph of parameter P₂ as a function of heat transfercoefficient h;

FIG. 12 is a graph of surface CS values of a glass-based article as afunction of thickness t, according to one or more embodiments of thepresent disclosure;

FIG. 13 is a graph showing CS as a function of thickness plotted forselected exemplary embodiments of glass-based article, after thermalstrengthening;

FIG. 14A is a perspective view of a glass-based article according to anexemplary embodiment;

FIG. 14B is a cross sectional illustration of some embodiments of thepresent disclosure;

FIG. 14C is a perspective view of additional embodiments of the presentdisclosure;

FIGS. 14D and 14E are cross sectional stress profiles of an exemplaryglass-based article according to some embodiments of the presentdisclosure;

FIG. 15 is a graph showing the DOC for Example 2, as a function of depthof layer;

FIG. 16 is a graph showing the ion exchange diffusion coefficient forExample 5, a function of temperature;

FIG. 17 is a graph showing the DOC of Example 6, as a function of thesquare root of ion exchange time and DOL;

FIG. 18 is a graph showing the concentration of Na₂O and K₂O in mol % ofExample 7A-3, as a function of depth;

FIG. 19 is a graph showing the concentration of Na₂O and K₂O in mol % ofExample 7A-4 as a function of depth;

FIG. 20 is a graph showing the concentration of Na₂O and K₂O in mol % ofExample 7A-5, as a function of depth;

FIG. 21 is a graph showing stress profiles of Comparative Example 7B-1and Examples 7B-5;

FIG. 22 is a graph showing stress profiles of Comparative Example 7B-2and Examples 7B-6;

FIG. 23 is a graph showing stress profiles of Comparative Example 7B-3and Examples 7B-7;

FIG. 24 is a graph showing stress profiles of Comparative Example 7B-4and Examples 7B-8;

FIG. 25 is a graph showing the CT values as a function of chemicalstrengthening duration of Comparative Examples 8B-1 through 7B-4,Comparative Examples 7C-1 through 7C-4 and Examples 7B-5 through 7B-8;

FIG. 26 is a graph plotting the change in CT as a function of chemicalstrengthening duration between Comparative Example 7B-1 and Example7B-5, between Comparative Example 7B-2 and Example 7B-6, betweenComparative Example 7B-3 and Example 7B-7, between Comparative Example7B-4 and Example 7B-8;

FIG. 27 is a graph plotting the surface CS and the CS at the DOL, as afunction of chemical strengthening time for each of Examples 7B-5through 7B-8;

FIG. 28 is a graph showing the CS at the DOL, as a function of as afunction of chemical strengthening time for each of Examples 7B-5through 7B-8, along with the change in CT from FIG. 26;

FIG. 29 is a graph showing the change in DOL of each of Examples 7B-5through 7B-8;

FIG. 30 is a graph showing the surface CS of Comparative Examples 7C-2through 7C-7 and Examples 7B-5 through 7B-8, as a function of chemicalstrengthening time;

FIG. 31 is a graph plotting the DOL of Comparative Examples 7C-2 through7C-7 and Examples 7B-5 through 7B-8, as a function of chemicalstrengthening time.

FIG. 32 is a graph plotting the CS at a depth equal to the DOL (or kneestress) of Comparative Examples 7C-2 through 7C-7 and Examples 7B-5through 7B-8, as a function of chemical strengthening time;

FIG. 33 shows the measured CT values of Examples 8A-2 through 8A-4,Examples 8B-2 through 8B-4 and Examples 8C-2 through 8C-4, shown as afunction of NaNO₃ concentration in the molten salt bath, and the initialCT values of each of the three samples of Comparative Examples 8A-1,8B-1 and 8C-1;

FIG. 34 is a graph showing the change in CT in absolute terms ofExamples 8A-2 through 8A-4, 8B-2 through 8B-4 and 8C-2 through 8C-4;

FIG. 35 is a graph showing the change in CT as a percent betweenComparative Example 8A-1 and Examples 8A-2 through 8A-4, betweenComparative Example 8B-1 and Examples 8B-2 through 8B-4, and betweenComparative Example 8C-1 and Examples 8C-2 through 8C-4;

FIG. 36 is a graph showing the surface CS and CS at a depth equal to theDOL (or knee CS) of Examples 8A-2 through 8A-3, Examples 8B-2 through8B-3 and Examples 8C-2 through 8C-3, as a function of NaNO₃concentration;

FIG. 37 is a graph showing the measured DOL values of Examples 8A-2through 8A-3, Examples 8B-2 through 8B-3 and Examples 8C-2 through 8C-3,plotted as a function of NaNO₃ concentration;

FIG. 38 is a bar graph showing (from left to right) the measured CT,surface CS, DOL and CS at DOL (or knee stress) of Examples 8B-2, 8B-5,8C-2 and 8C-5;

FIG. 39 is a graph showing the measured DOL for Examples 8B-2, 8B-5,8C-2 and 8C-5;

FIG. 40 is a graph showing the CT and surface CS of Examples 8B-5through 8B-8 and Examples 8C-5 through 8C-8, as a function of NaNO₃concentration;

FIG. 41 is a graph showing the surface CS as a function of CT ofExamples 8B-5 through 8B-8 and Examples 8C-5 through 8C-8;

FIG. 42 is a graph showing the measured stress as a function of depth ofExamples 8C-7 and 8C-8 and the stress profile of Comparative Example 8D;

FIG. 43 is a graph showing drop height test results for ComparativeExamples 9A, 9B, and Example 9C;

FIG. 44 is a graph showing failure probability for Comparative Examples9A, 9B, and Example 9C when subject to four point bend stress tofailure;

FIG. 45 is a graph showing failure probability for Comparative Examples9A, 9B, and Example 9C when subject to ring-on-ring stress to failure;

FIG. 46 is a schematic drawing of a ring-on-ring test set-up;

FIG. 47 is a graph showing ring-on-ring fracture strength forComparative Examples 9A, 9B, and Example 9C when first subject toabrasion with SiC particles using various pressures;

FIG. 48 is a graph showing drop height test results for ComparativeExamples 10A, 10B, and Example 10C;

FIG. 49 is a graph showing failure probability for Comparative Examples10A, 10B, and Example 10C when subject to four point bend stress tofailure;

FIG. 50 is a graph showing failure probability for Comparative Examples10A, 10B, and Example 10C when subject to ring-on-ring stress tofailure;

FIG. 51 is a graph showing ring-on-ring fracture strength forComparative Examples 10A, 10B, and Example 10C when first subject toabrasion with SiC particles using various pressures;

FIG. 52 is a plot of CT versus various initial temperature (T_(o)) forthe same heat transfer rate (h);

FIG. 53 is a plot of CS for various ion-exchange times and temperatureswith the same molten bath composition;

FIG. 54 is a plot of DOL for various ion-exchange times and temperatureswith the same molten bath composition;

FIG. 55A is a plan view of an exemplary electronic device incorporatingany of the strengthened articles disclosed herein; and

FIG. 55B is a perspective view of the exemplary electronic device ofFIG. 55A.

DETAILED DESCRIPTION

Traditional thermal glass strengthening methods are typically limited tothicker glass articles (typically sheets) because the level ofstrengthening depends on the temperature difference created between thesurface and the center of the glass article during quenching. Due tothermal conduction rate limitations of traditional strengtheningmethods, it is difficult to achieve significant temperature differencesbetween the surface and the center of a thin glass article due to therelatively even cooling that typically occurs throughout a thin glassarticle. Moreover, although traditional thermally strengthened glassarticles exhibit a DOC or a large CS region, such articles do notexhibit sufficiently high surface CS values needed for certainapplications. Specifically, traditional thermally strengthened glassarticles can achieve DOC values of about 21% of the thickness of sucharticles, but typically exhibit surface CS values of less than about 200MPa.

Conventional industrial processes for thermally strengthening glassinvolve heating glass substrates (typically sheets) in a radiant energyfurnace or a convection furnace (or a “combined mode” furnace using bothtechniques) to a predetermined temperature, then gas cooling(“quenching”), typically via convection by blowing large amounts ofambient air against or along the glass surface. This gas cooling processis predominantly convective, whereby the heat transfer is by mass motion(collective movement) of the fluid, via diffusion and advection, as thegas carries heat away from the hot glass substrate.

In conventional thermal strengthening processes, certain factors canrestrict the degree of strengthening in glass substrates, particularlyin thin glass substrates. Limitations exist, in part, because the amountof CS on the strengthened article is related directly to the magnitudein temperature differential between the surface and the center of thearticle, achieved during quenching; however, a temperature differentialduring quenching that is too large is likely to cause the glass to breakduring quenching. Breakage can be reduced, for a given rate of cooling,by starting the quench from a higher initial glass temperature.Moreover, greater strengthening can be achieved by quenching from ahigher temperature; however, increasing the temperature of the articleat the start of the quench can lead to excessive and undesirabledeformation of the article as it becomes softer.

In conventional thermal strengthening processes, substrate thicknessalso imposes significant limits on the achievable temperaturedifferential during quenching. The thinner the substrate, the lower thetemperature differential between the surface and the center for a givencooling rate during quenching. This is because there is less glassthickness to thermally insulate the center from the surface.Accordingly, thermal strengthening of thin glass substrates typicallyrequires higher cooling rates (as compared to thermal strengthening ofthicker glass substrates) and, thus, faster removal of heat from theexternal surfaces of the glass substrates typically requires significantenergy consumption in order to generate strengthening levels ofdifferential temperature between the inner and outer portions of theglass sheet.

By way of example, FIG. 1 shows the power required by air blowers (inkilowatts per square meter of glass substrate area) employed to blowsufficient ambient air to “fully temper” soda-lime glass (“SLG”)substrate in sheet form, as a function of glass thickness inmillimeters, based on industry standard thermal strengthening processesdeveloped 35 years ago. The power required increases exponentially asthe glass used gets thinner. Thus, glass substrates of about 3 mm inthickness were the thinnest fully thermally tempered commercial glassavailable for many years.

In conventional glass thermal strengthening processes, which useconvective gas, higher rates of cooling are achieved by increasing therate of air flow, decreasing the distance of air nozzle openings to theglass sheet surface, increasing the temperature of the glass (at thestart of cooling), and optionally, decreasing the temperature of thecooling air.

As a more recent example, the performance curves of FIG. 2 (Prior Art)were published using state of the art glass thermal strengtheningequipment. This improved equipment continues to use traditional airblown convective processes to cool the glass, but replaces rollers usedto support the glass during heating with a system that utilizes air tosupport the glass during at least the last stages of heating. Withoutroller contact, the glass can be heated to higher temperatures (andhigher softness/lower viscosity) prior to quenching, reportedly allowingthe production of fully tempered glass at 2 mm thickness. As shown inFIG. 2, the reported blower power required to strengthen a 2 mm thicksheet is reduced from 1200 kW/m² to 400 kW/m² at the higher temperaturesenabled by using air to support the glass (curve N) as compared to usingrollers (curve O).

Although it represents progress to be able to produce fully tempered 2mm thick glass, scaling the old and new curves O and N of FIG. 2 tomatch the scale of FIG. 1, as shown in FIG. 3 (Prior Art), shows thatthe improvement in performance achieved by the state of the artconvective tempering process (shown in FIG. 2) is relatively small andsimply an incremental change in the previous understanding of the energyneeds in convective strengthening of glass sheets. In FIG. 3 the old andnew curves O and N of FIG. 2 are scaled to match the graph of FIG. 1,and overlaid thereon (with the old curve O truncated at the top at 240kW/m² for easier viewing of the new curve N). From FIG. 3 it is apparentthat the technology represented by the curve N changes only slightly theperformance curve of convective gas quenching processes as glassthickness is decreased from 3 mm to 2 mm. The high operating point (400kW/m² of blower power for glass having a thickness of 2 mm) shows theextreme increase in power still required to process thinner glass bythis method. The sharp increase in airflow and, thus, power neededsuggests the difficulty, as a matter of both engineering practice andeconomics, with providing fully tempered glass having a thickness lessthan about 2 mm using conventional convective gas strengthening methods.Additionally, the very high airflows needed also could deform the shapeof thinner substrates.

Alternative thermal strengthening methods to current commercialconvective gas strengthening have been tried as well, but each hascertain drawbacks relative to convective gas strengthening. Inparticular, typical alternative thermal strengthening methods thatachieve higher cooling rates generally require at least some liquid orsolid contact with the glass surfaces, rather than gas contact only.Such contact with the glass substrate can adversely affect glass surfacequality, glass flatness, and/or evenness of the strengthening process.These defects sometimes can be perceived by the human eye, particularlywhen viewed in reflected light. As described in more detail below, atleast in some embodiments, the conductive thermal tempering system ofthe present disclosure reduces or eliminates such contact-relateddefects.

Liquid contact strengthening, in the form of immersion in liquid bathsor flowing liquids, as well as in the form of spraying, has been used toachieve higher cooling rates than convective gas strengthening, but hasthe drawback of causing excessive thermal variations across a sheetduring the cooling process. In immersion or immersion-like spraying orflowing of liquids, large thermal variations over small areas can occurdue to convection currents that arise spontaneously within the liquidbath or liquid flow. In finer spraying, the discrete spray droplets andthe effects of nozzle spray patterns also produce significant thermalvariations. Excessive thermal variations tend to cause glass breakageduring thermal strengthening by liquid contact, which can be mitigatedby limiting the cooling rates, but limiting cooling rates also lowersthe resulting strengths that can be achieved. Further, the necessaryhandling of the sheet (to position or hold it within the liquid bath orliquid flow or liquid spray) also causes physical stress and excessivethermal variations from physical contact with the sheet, tending also tocause breakage during strengthening and limiting the cooling rates andresulting strengths. Finally, some liquid cooling methods, such as highcooling rate quenching by oil immersion and various spraying techniques,can alter the glass surface during such cooling, requiring later removalof glass material from the sheet surface to produce a satisfactoryfinish.

Solid contact thermal strengthening involves contacting the surface ofthe hot glass with a cooler solid surface. As with liquid contactstrengthening, excessive thermal variations, like those seen in liquidcontact strengthening, can easily arise during the quenching process.Any imperfection in the surface finish of the glass substrate, in thequenching surfaces, or in the consistency of the thickness of thesubstrate, results in imperfect contact over some area of the substrate,and this imperfect contact may cause large thermal variations that tendto break the glass during processing and may also cause unwantedbirefringence if the sheet survives. Additionally, contacting the hotglass sheet with a solid object can lead to the formation of surfacedefects, such as chips, checks, cracks, scratches, and the like.Achieving good physical contact over the entirety of the surfaces of aglass substrate also can become increasing difficult as the dimensionsof the sheet increase. Physical contact with a solid surface also canmechanically stress the sheet during quenching, adding to the likelihoodof breaking the sheet during the process. Further, the extreme high ratetemperature changes at the initiation of contact can cause breakageduring sheet processing and, as such, contact cooling of thin glasssubstrates has not been commercially viable.

Although chemical strengthening is not limited by the thickness of theglass-based article in the same manner as thermal strengtheningprocesses, known chemically strengthened glass-based articles do notexhibit the stress profile (i.e., stress as a function of thickness ofdepth from a major surface) of thermally tempered glass-based articles.An example of a stress profile generated by chemical strengthening(e.g., by an ion exchange process), is shown in FIG. 4. In FIG. 4, thechemically strengthened glass-based article 200 includes a first surface201, a thickness t₂ and a surface CS 210. The glass-based article 200exhibits a CS that decreases generally from the first surface 201 to aDOC 230, as defined herein, at which depth the stress changes fromcompressive to tensile stress and then reaches a maximum CT 220. Asshown in FIG. 4, such profiles exhibit a substantially flat CT region ora CT region with a constant or near constant tensile stress along atleast a portion of the CT region. Known chemically strengthenedglass-based articles exhibit a significantly lower DOC value and canoften exhibit a lower maximum CT value, as compared to known thermallystrengthened glass-based articles. Deeper DOC values may be obtainablebut only after long ion exchange processes, which can also cause stressrelaxation and thus lower surface CS values.

Embodiments of the present disclosure include thin glass-based articlesthat exhibit a DOC that is comparable or even greater than thick glassarticles that are thermally strengthened using conventional thermalstrengthening processes, while exhibiting a high surface CS (e.g.,greater than about 200 MPa, greater than about 300 MPa or greater thanabout 400 MPa, as described herein). This combination of high surface CSvalues and deep DOC is not exhibited by glass articles strengthenedusing known thermal strengthening processes alone or in combination withchemical strengthening. More particularly, the thermal strengtheningprocess described herein generates a deep parabolic stress profile whichprevents penetration of deep flaws and fatigue (i.e., repeated damage)of the glass-based article. In addition, the subsequent chemicalstrengthening process generates a large or high surface compression,which is unachievable by thermal tempering. A high surface CS valueprevents formation and penetration of surface flaws, scratching, andperhaps crack initiation. If performed correctly, the combination of thethermal strengthening process described herein and chemicalstrengthening provides a large surface compression to a depth sufficientto cover edge flaws, while the thermal strengthening process allows thecompression to extend to 20% or more of the glass-based articlethickness and provide protection against flaw growth as a result ofrepeated damage. Moreover, such glass-based articles may be thermallystrengthened using the processes and systems described herein in lessthan 1 minute or even less than 30 seconds, and chemically strengthenedin about 3 hours or less.

The present disclosure surpasses the traditional processes describedabove to effectively, efficiently, and evenly thermally strengthen andchemically strengthened thin glass substrates at commercial scaleswithout generating various flaws common in conventional thermalstrengthening processes, e.g., without damaging the surface of theglass, without inducing birefringence, without uneven strengthening,and/or without causing unacceptable breakage, etc.

The thermal strengthening systems and processes discussed herein utilizevery high heat transfer rates (h in units of cal/cm²-s-C°) in a precisemanner, with good physical control and gentle handling of the glass. Inparticular embodiments, the thermal strengthening processes and systemsdiscussed herein utilize a small-gap, gas bearing in thecooling/quenching section that allows processing thin glass substratesat higher relative temperatures at the start of cooling, resulting inhigher thermal strengthening levels. As described below, this small-gap,gas bearing cooling/quenching section achieves very high heat transferrates via conductive heat transfer to heat sink(s) across the gap,rather than using high air flow based convective cooling. This high rateconductive heat transfer is achieved while not contacting the glass withliquid or solid material, by supporting the glass substrate on gasbearings within the gap.

In one or more embodiments, the resulting thermally strengthenedglass-based articles exhibit higher levels of permanent thermallyinduced stresses than previously known. Without wishing to be bound bytheory, it is believed that the achieved levels of thermally inducedstress are obtainable for a combination of reasons. The high uniformityof the heat transfer in the processes detailed herein reduces or removesphysical and unwanted thermal stresses in the glass, allowing glasssubstrates to be tempered at higher heat transfer rates withoutbreaking. Further, the present methods can be performed at lower glasssubstrate viscosities (higher initial temperatures at the start ofquench), while still preserving the desired glass flatness and form,which provides a much greater change in temperature in the coolingprocess, thus increasing the heat strengthening levels achieved.

The thermally strengthened glass-based articles are then chemicallystrengthened in a molten salt bath to generate a high surface CS.Without being bound by theory, the chemical strengthening process can betailored to provide a “spike” or to increase the slope of the stressprofile at or near the surface of the resulting glass-based article toprovide a high surface CS, which complements the deep DOC generated bythe thermal strengthening process described herein.

As used herein, embodiments of the chemical strengthening include an ionexchange process. In this process, ions at or near the surface of theglass-based substrate or thermally strengthened glass-based article arereplaced by—or exchanged with—larger ions having the same valence oroxidation state. In those embodiments in which the glass-based substrateor thermally strengthened glass-based article comprises an alkalialuminosilicate glass, ions in the surface layer of the glass and thelarger ions are monovalent alkali metal cations, such as Li⁺ (whenpresent in the glass-based substrate or thermally strengthenedglass-based article), Na⁺, K⁺, Rb⁺, and Cs⁺. Alternatively, monovalentcations in the surface layer may be replaced with monovalent cationsother than alkali metal cations, such as Ag⁺ or the like.

Ion exchange processes are typically carried out by immersing aglass-based substrate or thermally strengthened glass-based article in amolten salt bath (or two or more molten salt baths) containing thelarger ions to be exchanged with the smaller ions in the glass-basedsubstrate or thermally strengthened glass-based article. It should benoted that aqueous salt baths may also be utilized. In some instances, aspray process can be used to apply a salt solution to the glass-basedsubstrate or a thermally strengthened glass-based article, which is thenheated to promote ion exchange. The composition of the bath(s) and/orsolutions may include more than one type of larger ion (e.g., Na+ andK+) or a single larger ion. It will be appreciated by those skilled inthe art that parameters for the ion exchange process, including, but notlimited to, bath/spray solution composition and temperature, immersiontime, the number of immersions of the glass-based article in a salt bath(or baths), number of applications of salt solutions, use of multiplesalt baths or solutions, additional steps such as annealing, washing,and the like, are generally determined by the composition of theglass-based substrate and/or article (including the structure of thearticle and any crystalline phases present) and the desired DOL, DOC, CTand/or surface CS of the glass-based article that results fromstrengthening. By way of example, ion exchange of thermally strengthenedglass-based articles may be achieved by immersion of the glass-basedsubstrates in at least one molten bath containing a salt such as, butnot limited to, nitrates, sulfates, and chlorides of the larger alkalimetal ion. Typical nitrates include KNO₃, NaNO₃, and LiNO₃, andcombinations thereof. The temperature of the molten salt bath typicallyis in a range from about 380° C. up to about 450° C., while immersiontimes range from about 10 minutes up to about 5 hours (e.g., from about10 minutes to about 1 hour) depending on glass thickness, bathtemperature and glass diffusivity. However, temperatures and immersiontimes different from those described above may also be used.

In one or more embodiments, the thermally strengthened glass-basedarticle may be immersed in a molten salt bath of 100% KNO₃ having atemperature from about 370° C. to about 480° C. (e.g., 410° C.). In oneor more embodiments, the thermally strengthened glass-based article maybe immersed in a molten salt bath of 100% NaNO₃ having a temperaturefrom about 370° C. to about 480° C. In some embodiments, the thermallystrengthened glass-based article may be immersed in a molten mixed saltbath including from about 5% to about 90% KNO₃ and from about 10% toabout 95% NaNO₃. In some instances, the molten mixed salt bath mayinclude form about 50% to about 100% NaNO₃, with the balance (if any)including KNO₃. The mixed salt bath may have a temperature in the rangefrom about 380° C. to about 420° C. In some embodiments, the thermallystrengthened glass-based article may be immersed in a molten mixed saltbath including Na₂SO₄ and NaNO₃ and have a wider temperature range(e.g., up to about 500° C.). In one or more embodiments, the glass-basedarticle may be immersed in a second bath, after immersion in a firstbath. Immersion in a second bath may include immersion in a molten saltbath including 100% KNO₃ for 15 minutes to 8 hours.

In one or more embodiments, the thermally strengthened glass-basedarticle may be immersed in a molten, mixed salt bath including NaNO₃ andKNO₃ (e.g., 49% NaNO₃/51% KNO₃, 50% NaNO₃/50% KNO₃, 51% NaNO₃/49% KNO₃,95% KNO₃/5% NaNO₃, 90% KNO₃/10% NaNO₃, or 80% KNO₃/20% NaNO₃) having atemperature less than about 420° C. (e.g., about 400° C. or about 380°C.) for less than about 5 hours, or even about 4 hours or less.

In some embodiments, chemical strengthening may be performed by ionimplantation processes. For example, the thermally strengthenedglass-based article may be placed in a vacuum chamber and subjected toan ion implantation process by which a strengthening ion or an ion thatis capable of generating a compressive stress in the glass is implantedinto the thermally strengthened glass-based article. The implantationdepth would correlate to the DOL values recited herein. In one or moreembodiments, the strengthening ion may be any ion that creates acrowding effect that generates a compressive stress.

The resulting stress profile generated by the thermal strengtheningprocess and the subsequent chemical strengthening process describedherein is illustrated in FIG. 5. The glass-based article of one or moreembodiments includes a thermally strengthened region 310 including astress induced by thermal strengthening and a chemically strengthenedregion 320 including a stress induced by chemical strengthening. Thesurface CS is generated by the combination of stress induced by thermalstrengthening and stress induced by chemical strengthening. The stressinduced by thermal strengthening (or the thermally strengthened region)extends to the DOC indicated by 312. The stress induced by chemicalstrengthening (or the chemically strengthened region) extends to a DOLindicated by 322 (in some instances, this DOL is referred to as a “knee”of the stress profile). The CT balances the CS portions of the stressprofile.

In some embodiments, the stress profile exhibits a parabolic-like shape.In one or more embodiments, the parabolic-like shape is exhibited alongthe stress profile region or depth of the glass-based article exhibitingtensile stress. In one or more specific embodiments, the stress profileis free of a flat stress (i.e., compressive or tensile) portion or aportion that exhibits a substantially constant stress (i.e., compressiveor tensile). In some embodiments, the CT region exhibits a stressprofile that is substantially free of a flat stress or free of asubstantially constant stress. In one or more embodiments, all points ofthe stress profile 312 between the entire thickness or along a thicknessrange from about 0t up to about 0.2●t and greater than 0.8●t (or fromabout 0●t to about 0.3●t and greater than 0.7.0 comprise a tangent thatis less than about −0.1 MPa/micrometers or greater than about 0.1MPa/micrometers. In some embodiments, the tangent may be less than about−0.2 MPa/micrometers or greater than about 0.2 MPa/micrometers. In somemore specific embodiments, the tangent may be less than about −0.3MPa/micrometers or greater than about 0.3 MPa/micrometers. In even morespecific embodiments, the tangent may be less than about −0.5MPa/micrometers or greater than about 0.5 MPa/micrometers. In otherwords, the stress profile of one or more embodiments along thesethickness ranges (i.e., the entire thickness, along the range from about0●t up to about 0.2●t and greater than 0.8t, or along the range fromabout 0t to about 0.3●t and 0.7●t or greater) exclude points having atangent, as described herein. Without being bound by theory, known errorfunction or quasi-linear stress profiles have points along thesethickness ranges (i.e., from about 0●t up to about 2●t and greater than0.8●t, or from about 0●t to about 0.3●t and 0.7●t or greater) that havea tangent that is flat or has zero slope stress profile along asubstantial portion of such thickness ranges, as shown in FIG. 4, 220).The glass-based articles of one or more embodiments of this disclosuredo not exhibit such a stress profile having a flat or zero slope stressprofile along these thickness ranges, as shown in FIG. 5.

In one or more embodiments, the glass-based article exhibits a stressprofile in a thickness range from about 0.1●t to 0.3●t and from about0.7●t to 0.9●t that comprises a maximum tangent and a minimum tangent.In some instances, the difference between the maximum tangent and theminimum tangent is about 3.5 MPa/micrometers or less, about 3MPa/micrometers or less, about 2.5 MPa/micrometers or less, or about 2MPa/micrometers or less.

In one or more embodiments, the glass-based article includes a stressprofile that is substantially free of any flat segments that extend in adepth direction or along at least a portion of the thickness t of theglass-based article. In other words, the stress profile is substantiallycontinuously increasing or decreasing along the thickness t. In someembodiments, the stress profile is substantially free of any flatsegments in a depth direction having a length of about 10 micrometers ormore, about 50 micrometers or more, or about 100 micrometers or more, orabout 200 micrometers or more. As used herein, the term “flat” refers toa slope having a magnitude of less than about 5 MPa/micrometer, or lessthan about 2 MPa/micrometer along the linear segment. In someembodiments, one or more portions of the stress profile that aresubstantially free of any flat segments in a depth direction are presentat depths within the glass-based article of about 5 micrometers orgreater (e.g., 10 micrometers or greater, or 15 micrometers or greater)from either one or both the first surface or the second surface. Forexample, along a depth of about 0 micrometers to less than about 5micrometers from the first surface, the stress profile may includelinear segments, but from a depth of about 5 micrometers or greater fromthe first surface, the stress profile may be substantially free of flatsegments.

In some embodiments, the stress profile may include linear segments atdepths from about 0t up to about 0.1t and may be substantially free offlat segments at depths of about 0.1t to about 0.4t. In someembodiments, the stress profile from a thickness in the range from aboutOtto about 0.1t may have a slope in the range from about 20 MPa/micronsto about 200 MPa/microns. As will be described herein, such embodimentsmay be formed using a single ion-exchange process by which the bathincludes two or more alkali salts or is a mixed alkali salt bath ormultiple (e.g., 2 or more) ion exchange processes.

In some embodiments, the glass-based articles exhibit the stressprofiles described herein, while still exhibiting a deep DOC and highsurface CS.

In some embodiments, the chemically induced CS region is referred to asa first CS region that includes a concentration of a metal oxide that isboth non-zero and varies along a portion of the thickness of theglass-based article. In one or more embodiments, the thermally inducedCS region is referred to as a second CS region. Referring to FIG. 5, inone or more embodiments, the first CS region 304 extends from a firstsurface 301 to the second CS region 306. The second CS region 306extends from the first CS region 304 to the DOC 312. In some instances,the second CS region 306 is between the first CS region 304 and the CTregion 308. In some embodiments, the entire second CS region includes aconstant metal oxide concentration region. In some embodiments, only aportion of the second CS region includes a constant metal oxide region,while the remaining portion includes a varying metal oxideconcentration. In one or more embodiments, the metal oxide having avarying concentration in the first CS region and/or the second CS regiongenerates a stress along the specified thickness range or beyond thespecified thickness range along which the concentration metal oxidevaries. In other words, the stress profile along the chemically inducedCS region may be generated due to a non-zero concentration of a metaloxide(s) that varies along a portion of the thickness. In someembodiments, this metal oxide may have the largest ionic diameter of allof the total metal oxides in the glass-based article. In other words,the metal oxide having a varying concentration may be the metal oxidethat is ion exchanged into the glass-based article. The metal oxide thatis non-zero in concentration and varies along a portion of the thicknessmay be described as generating a stress in the glass-based article.

The variation in concentration of metal oxide may be continuous alongthe above-referenced thickness ranges. Variation in concentration mayinclude a change in metal oxide concentration of about 0.2 mol % orgreater along a thickness segment of about 100 micrometers. This changemay be measured by known methods in the art including microprobe.

The variation in concentration of metal oxide may be continuous alongthe above-referenced thickness ranges. In some embodiments, thevariation in concentration may be continuous along thickness segments inthe range from about 10 micrometers to about 30 micrometers. In someembodiments, the concentration of the metal oxide decreases from thefirst surface to a point between the first surface and the secondsurface.

The concentration of metal oxide may include more than one metal oxide(e.g., a combination of Na₂O and K₂O). In some embodiments, where twometal oxides are utilized and where the respective diameters of the ionsdiffer from one or another, the concentration of ions having a largerdiameter is greater than the concentration of ions having a smallerdiameter at shallow depths, while the at deeper depths, theconcentration of ions having a smaller diameter is greater than theconcentration of ions having larger diameter. For example, where asingle Na- and K-containing bath is used in the ion exchange process,the concentration of K+ ions in the glass-based article is greater thanthe concentration of Na+ ions at shallower depths, while theconcentration of Na+ is greater than the concentration of K+ ions atdeeper depths. This is due, in part, due to the size of the ions. Insuch glass-based articles, the area at or near the surface comprises agreater CS due to the greater amount of larger ions (i.e., K+ ions) ator near the surface. This greater CS may be exhibited by a stressprofile having a steeper slope at or near the surface (i.e., a spike inthe stress profile at the surface).

The concentration gradient or variation of one or more metal oxides iscreated by chemically strengthening a glass-based substrate, aspreviously described herein, in which a plurality of first metal ions inthe glass-based substrate is exchanged with a plurality of second metalions (i.e., the second metal ions are ion exchanged into the glass-basedsubstrate during chemical strengthening). The first ions may be ions oflithium, sodium, potassium, and rubidium. The second metal ions may beions of one of sodium, potassium, rubidium, and cesium, with the provisothat the second alkali metal ion has an ionic diameter greater than theionic diameter of the first alkali metal ion. The second metal ion,which is ion exchanged into the glass-based substrate after chemicalstrengthening, is present in the glass-based substrate as an oxidethereof (e.g., Na₂O, K₂O, Rb₂O, Cs₂O or a combination thereof). Thesecond metal ion generates the stress in the glass-based article.

Where two metal ions are exchanged into the glass-based article (i.e.,where a mixed salt bath or more than one salt bath is used during thechemical strengthening process), one metal ion may extend along a firstCS region, while the second metal ion may extend along the first CSregion and a second CS region, such that the second CS region issubstantially free of the first metal ion (or a concentration gradientthereof). In the glass-based article, this differential diffusion isdetected by a non-zero and varying concentration of an oxide of thefirst metal ion (i.e., a first metal oxide) along the first CS regiononly and the second CS region being substantially free of the firstmetal oxide. One way to describe this type of compositional differenceis to characterize the relative sizes of the first metal ion and thesecond metal ion. For example, the first metal ion may have a diameterthat is larger than the second metal ion, and may have a diameter thatis the largest of all the metal ions in the glass-based article.Accordingly, the second CS region may be free of the metal ions havingthis largest diameter. In some embodiments, first CS region may have adifferent composition from the second CS region due to the presence ofboth the first metal ion (or oxide thereof) and second metal ion (oroxide thereof) in the first CS region, while the second CS region onlyincludes the second metal ion (or oxide thereof). In some embodiments,the glass-based article includes a central tension region that also hasa different composition from the first CS region. In some embodiments,the central tension region and the second CS region have the samecomposition as one another, which differs from the composition of thefirst CS region. In such embodiments, the first metal oxide may includeNa₂O, K₂O, Rb₂O or Cs₂O, while the second metal oxide may include Li₂O,Na₂O, K₂O, or Rb₂O as long as the second metal ion of the second metaloxide has a diameter that is smaller than the first metal ion of thefirst metal oxide.

In one or more embodiments, the concentration of the varying andstrengthening metal oxide is about 0.5 mol % or greater. In someembodiments, the concentration of the metal oxide may be about 0.5 mol %or greater (e.g., about 1 mol % or greater) along the entire thicknessof the glass-based article, and is greatest at the first surface and/orthe second surface and decreases substantially constantly to a pointbetween the first surface and the second surface. The totalconcentration of the particular metal oxide in the glass-based articlemay be in the range from about 1 mol % to about 20 mol %.

The concentration of the metal oxide may be determined from a baselineamount of the metal oxide in the glass-based article prior to beingchemically strengthened to include the concentration gradient of suchmetal oxide.

The combination of deep DOC and high surface CS values is not exhibitedby known thermally and chemically strengthened glass-based articlesbecause the subsequent chemical strengthening processes causes stressrelaxation or release, which causes a decrease in the DOC. Without beingbound by theory, a higher fictive temperature in a thermallystrengthened glass-based article would cause more rapid stressrelaxation and thus, a decrease in DOC after subsequent chemicalstrengthening. Surprisingly, the thermal strengthening process describedherein generates an even higher fictive temperature in the thermallystrengthened glass-based article (due to the use of very high heattransfer rates), which enables maintenance of the DOC after subsequentchemical strengthening. In known thermal strengthening processes, theresulting DOC level is shown to decrease significantly after subsequentchemical strengthening due to stress relaxation because the DOC achievedthrough conventional thermal strengthening is not as great as isachieved by the thermal strengthening methods described herein. In someinstances, the properties of the glass-based article after thermalstrengthening as described herein also enable generation of DOC in theglass-based substrate beyond depths of ion penetration. For example, theDOC is greater than 20% or up to and including about 24% of thethickness, whereas the ion penetration from the subsequent chemicalstrengthening is less than the DOC. In some instances, some ionspenetrate to the DOC and may contribute some stress.

The thermal strengthening process described herein increases the fictivetemperature of the resulting glass article and creates a more openstructure (when compared to the glass substrate prior to thermalstrengthening). This allows for an increased rate of chemicalstrengthening (and in particular ion exchange), leading to a deeper DOL.In some embodiments, a deeper DOL may result in a lower surface CSgenerated by chemical strengthening, but this lower surface CS iscompensated by the initial CS generated and present from the thermalstrengthening process. As the two strengthening mechanisms work byfundamentally different processes, they are not mutually exclusive, andthe strengthening effects can be added together. In known thermal andchemical strengthened glass articles, the strengthening mechanismsinfluence each other and the later chemical strengthening processreduces the strength imparted by the earlier thermal strengtheningprocess. In some embodiments, the surface CS exhibited by theglass-based articles described herein can even exceed the surface CSgenerated by known chemical strengthening processes alone.

The glass-based articles described herein also exhibit higher damagetolerance or resistance. In particular, the glass-based articles exhibita higher fictive temperature and more open structure after beingsubjected to the thermal strengthening process described herein, whicheach or both increase the indentation cracking threshold of theglass-based article. In some embodiments, the chemical strengtheningprocess is performed such that the fictive temperature does notsignificantly relax during such treatment, and thus, this benefit of ahigh fictive temperature can carry over to the finished thermallystrengthened and chemically strengthened glass-based article.

Moreover, in one or more embodiments, the glass-based article can bestrengthened at a significantly lower cost and more quickly than knownstrengthening processes. In particular, the thermal strengtheningprocesses described herein promote faster ionic diffusion during thesubsequent chemical strengthening process. Accordingly, much shorterchemical strengthening processes can be utilized to achieve a desiredDOL. In addition, glasses in which it would typically not be consideredideal for chemical strengthening processes, such as in soda-limesilicate glass or some alkali aluminosilicate glasses, can now bechemically strengthened to a desired performance level. For example, aknown alkali aluminosilicate glass having a nominal composition of 69mol % SiO₂, 8.5 mol % Al₂O₃, 14 mol % Na₂O, 1.2 mol % K₂O, 6.5 mol %MgO, 0.5 mol % CaO, and 0.2 mol % SnO₂ requires 5.5 hours of chemicalstrengthening in a 420° C. molten salt bath for sufficient strengthening(i.e., such that the resulting glass-based article exhibits a surface CSin excess of 700 MPa and a DOL in the range from about 42 micrometers toabout 44 micrometers). The same glass having the same thickness can bethermally strengthened using the process described herein according toone or more embodiments for about 15 seconds and then chemicallystrengthened in a 410° C. molten salt bath, resulting in a glass-basedarticle exhibiting superior strengthening and performance compared tothe glass-based article that is subjected to 5.5 hours of chemicalstrengthening alone.

Referring to FIGS. 6 and 7, a thermally strengthened and chemicallystrengthened glass-based article a high surface CS and deep DOC is shownaccording to an exemplary embodiment. FIG. 6 shows a perspective view ofthe thermally strengthened and chemically strengthened glass-basedarticle 500, and FIG. 7 a diagrammatic partial cross-section ofthermally strengthened glass sheet 500 according to one or moreembodiments.

As shown in FIG. 6, a thermally strengthened and chemically strengthenedglass-based article 500 (e.g., sheet, beam, plate), includes a firstsurface 510, a second surface 520 (dotted line to back side of the sheet500, which may be translucent as disclosed herein), and a body 522extending therebetween. The second surface 520 is on an opposite side ofthe body 522 from the first surface 510 such that a thickness t of thestrengthened glass-based article 500 is defined as a distance betweenthe first and second surfaces 510, 520, where the thickness t is also adimension of depth. A width, w, of the strengthened glass-based article500 is defined as a first dimension of one of the first or secondsurfaces 510, 520 orthogonal to the thickness t. A length, l, of thestrengthened glass or glass-ceramic sheet 500 is defined as a seconddimension of one of the first or second surfaces 510, 520 orthogonal toboth the thickness t and the width w.

In exemplary embodiments, thickness t of glass-based article 500 is lessthan length l of glass-based article 500. In other exemplaryembodiments, thickness t of glass-based article 500 is less than width wof glass-based article 500. In yet other exemplary embodiments,thickness t of glass-based article 500 is less than both length l andwidth w of glass sheet 500. As shown in FIG. 7, glass-based article 500further has regions of permanent thermally induced CS 530 and 540 atand/or near the first and second surfaces 510, 520 extending to a DOC560, regions of chemically induced CS 534 and 544 at and/or near thefirst and second surfaces 510, 520 extending to a DOL 570 and balancedby a region of permanent thermally induced central tensile stress 550(i.e., tension) in the central portion of the sheet.

In various embodiments, thickness t of the glass-based article 500ranges from 0.1 mm to 5.7 or 6.0 mm, including, in addition to the endpoint values, 0.2 mm, 0.28 mm, 0.4 mm, 0.5 mm, 0.55 mm, 0.7 mm, 1 mm,1.1 mm, 1.5 mm, 1.8 mm, 2 mm, and 3.2 mm.

Contemplated embodiments include thermally strengthened glass sheets 500having thicknesses tin ranges from 0.1 to 20 mm, from 0.1 to 16 mm, from0.1 to 12 mm, from 0.1 to 8 mm, from 0.1 to 6 mm, from 0.1 to 4 mm, from0.1 to 3 mm, from 0.1 to 2 mm, from 0.1 to less than 2 mm, from 0.1 to1.5 mm, from 0.1 to 1 mm, from 0.1 to 0.7 mm, from 0.1 to 0.5 mm andfrom 0.1 to 0.3 mm.

In some embodiments, glass-based article of 3 mm or less in thicknessare used. In some embodiments, the glass-based article thickness isabout (e.g., plus or minus 1%) 8 mm or less, about 6 mm or less, about 3mm or less, about 2.5 mm or less, about 2 mm or less, about 1.8 mm orless, about 1.6 mm or less, about 1.4 mm or less, about 1.2 mm or less,about 1 mm or less, about 0.8 mm or less, about 0.7 mm or less, about0.6 mm or less, about 0.5 mm or less, about 0.4 mm or less, about 0.3 mmor less, or about 0.28 mm or less.

In some embodiments, thermally strengthened and chemically strengthenedglass-based article have high aspect ratios—i.e., the length and widthto thickness ratios are large. Because the thermal strengtheningprocesses discussed herein do not rely on high pressures or largevolumes of air, desirable surface roughness and flatness, can bemaintained after tempering without contact between one or both majorsurfaces of the glass-based article and a solid or liquid (e.g., byincluding a gap between the one or both major surfaces of theglass-based article and a solid or liquid, wherein the gap is free ofsolid matter or includes a gas), and by the use of high thermal transferrate systems discussed herein. Similarly, the thermal and chemicalstrengthening processes discussed herein allow high aspect ratio glasssheets (i.e., glass sheets with high ratio of length to thickness, or ofwidth to thickness, or both) to be strengthened while retaining thedesired or necessary shape. Specifically, glass-based articles caninclude sheets with length to thickness and/or width to thickness ratios(“aspect ratios”) of approximately at least 10:1, at least 20:1, and upto and over 1000:1 can be strengthened. In contemplated embodiments,sheets with aspect ratios of at least 200:1, at least 500:1, at least1000:1, at least 2000:1, at least 4000:1 can be strengthened.

According to an exemplary embodiment, the length l of the thermallystrengthened and chemically strengthened glass-based article 500 isgreater than or equal to the width w, such as greater than twice thewidth w, greater than five times the width w, and/or no more than fiftytimes the width w. In some such embodiments, the width w of thethermally strengthened and chemically strengthened glass-based article500 is greater than or equal to the thickness t, such as greater thantwice the thickness t, greater than five times the thickness t, and/orno more than fifty times the thickness t.

In some embodiments, the length l of the thermally strengthened andchemically strengthened glass-based article 500 is at least 1 cm, suchas at least 3 cm, at least 5 cm, at least 7.5 cm, at least 20 cm, atleast 50 cm, and/or no more than 50 m, such as no more than 10 m, nomore than 7.5 m, no more than 5 m. In some such embodiments, the width wof the thermally strengthened and chemically strengthened glass-basedarticle 500 is at least 1 cm, such as at least 3 cm, at least 5 cm, atleast 7.5 cm, at least 20 cm, at least 50 cm, and/or no more than 50 m,such as no more than 10 m, no more than 7.5 m, no more than 5 m.Referring to FIG. 6, the thermally strengthened and chemicallystrengthened glass-based article is in the form of a sheet 500 has athickness t that is thinner than 5 cm, such as 2.5 cm or less, 1 cm orless, 5 mm or less, 2.5 mm or less, 2 mm or less, 1.7 mm or less, 1.5 mmor less, 1.2 mm or less, or even 1 mm or less in contemplatedembodiments, such as 0.8 mm or less, such as 0.7 mm or less, such as 0.6mm or less, such as 0.5 mm or less, such as 0.4 mm or less, such as 0.3mm or less, such as 0.28 mm or less; and/or the thickness t is at least10 μm, such as at least 50 μm, at least 100 μm, at least 300 μm.

In other contemplated embodiments, the thermally strengthened andchemically strengthened glass-based article may be sized other than asdisclosed herein. In contemplated embodiments, the length l, width w,and/or thickness t of the thermally strengthened and chemicallystrengthened glass-based article may vary, such as for more complexgeometries, where dimensions disclosed herein at least apply to aspectsof the corresponding glass or glass-ceramic articles having theabove-described definitions of length l, width w, and thickness t withrespect to one another.

In some embodiments, at least one of the first or second surfaces 510,520 of thermally strengthened and chemically strengthened glass-basedarticle 500 has a relatively large surface area. In various embodiments,first and/or second surfaces 510, 520 having areas of 100 mm² orgreater, such about 900 mm² or greater, about 2500 mm² or greater, 5000mm² or greater, about 100 cm² or greater, about 500 cm² or greater,about 900 cm² or greater, about 2500 cm² or greater, or about 5000 cm²or greater. The upper limit of the first or second surfaces 510, 520 isnot particularly limited. In some embodiments, the first or secondsurfaces 510, 520 may have a surface area of no more than 2500 m², nomore than 100 m², no more than 5000 cm², no more than 2500 cm², no morethan 1000 cm², no more than 500 cm², or no more than 100 cm². As such,the thermally strengthened and chemically strengthened glass-basedarticle 500 may have a relatively large surface area; which, except bymethods and systems disclosed herein, may be difficult or impossible tothermally strengthen particularly while having the thicknesses, surfacequalities, and/or strain homogeneities of the glass sheets discussedherein. Further, except by methods and systems disclosed herein, it maybe difficult or impossible to achieve the stress profile, particularlythe negative tensile stress portion of the stress profile (see generallyFIG. 5), without relying upon ion-exchange or a change in the type ofglass.

As noted above, the thermally strengthened and chemically strengthenedglass-based article discussed herein may have surprisingly high surfaceCS values, surprisingly high central tensile stresses, surprisingly deepDOC values, and/or unique stress profiles (see FIG. 5). This isparticularly true considering the low thickness and/or other uniquephysical properties (e.g., very low roughness, high degree of flatness,various optical properties, fictive temperature properties, etc.) ofthermally strengthened and chemically strengthened glass-based article500 as discussed herein.

CS values of the thermally strengthened and chemically strengthenedglass-based articles described herein (e.g., in regions 530, 540 shownin FIG. 5) can vary as a function of thickness t of the glasses. Invarious embodiments, the thermally strengthened and chemicallystrengthened glass-based article may have a thickness of 3 mm or less(e.g., 2 mm or less, 1.2 mm or less, 1 mm or less, 0.9 mm or less, 0.8mm or less, 0.7 mm or less, 0.6 mm or less, 0.5 mm or less, 0.4 mm orless, 0.3 mm or less, or 0.28 mm or less) and a surface CS of about 300MPa or greater, about 400 MPa or greater, 500 MPa or greater, 600 MPa orgreater, about 700 MPa or greater, about 800 MPa or greater, about 900MPa or greater, or even about 1 GPa or greater. The upper limit of thesurface CS may be about 2 GPa. In some embodiments, the thermallystrengthened and chemically strengthened glass-based article exhibits aCS value at the depth equal to the DOL (or a “knee stress” or “knee CS”)of about 150 MPa or greater (e.g., about 175 MPa or greater, about 200MPa or greater or about 225 MPa or greater). In such embodiments, theDOL at which the knee stress is 150 MPa or greater may be about 10micrometers or greater (e.g., 12 micrometers or greater, 14 micrometersor greater, 15 micrometers or greater, or 17 mircometers or greater, or19 micrometers or greater or 21 micrometers or greater, or 24micrometers or greater). The DOL at which the knee stress is 150 MPa orgreater may be expressed as a function of thickness of the glass-basedarticle. In such embodiments, the DOL at which the knee stress is 150MPa or greater may be about 0.01●t or greater. CS and DOL may bemeasured using an FSM technique as described herein.

In various embodiments, the thermally strengthened and chemicallystrengthened glass-based article may have a CT of about 30 MPa orgreater, about 40 MPa or greater, about 50 MPa or greater, about 60 MPaor greater, about 70 MPa or greater or about 80 MPa or greater. These CTvalues may be present while the thermally and chemically strengthenedglass-based article has a thickness of 3 mm or less (e.g., 2 mm or less,1.2 mm or less, 1 mm or less, 0.9 mm or less, 0.8 mm or less, 0.7 mm orless, 0.6 mm or less, 0.5 mm or less, 0.4 mm or less, 0.3 mm or less, or0.28 mm or less). As used herein, CT refers to the absolute maximum CTin the glass-based article. In one or more specific embodiments, the CTvalue of the glass-based article may be greater than about 100 MPa. Inother embodiments, the CT of the thermally strengthened and chemicallystrengthened glass-based article may be less than 400 MPa, or less than300 MPa. In some embodiments, the CT may be from about 30 MPa to about300 MPa, about 60 MPa to about 200 MPa, about 70 MPa to about 150 MPa,or about 80 MPa to about 140 MPa. Because very high-heat transfer ratescan be applied via the systems and methods discussed herein, significantthermal effects, for example CT values of at least 10 or even at least20 MPa, can be produced in sheets of SLG of less than 0.3 mm thickness.In fact, very thin sheets, sheets at least as thin as 0.1 mm, can bethermally and chemically strengthened. In one or more embodiments, CTvalues may be measured using a scattered light polariscope (SCALP),using techniques known in the art.

Believed unique to the present disclosure, given relatively largesurface areas and/or thin thicknesses of the thermally strengthened andchemically strengthened glass-based article 500 as disclosed herein,tensile stress in the stress profile 560 sharply transitions between thepositive tensile stress of the interior portion 550 and the negativetensile stress of the portions 530, 540 exterior to and adjoining theinterior portion 550. This sharp transition may be understood as a rateof change (i.e., slope) of the tensile stress which may be expressed asa magnitude of stress (e.g., 100 MPa, 200 MPa, 250 MPa, 300 MPa, 400MPa, a difference in peak values of the positive and negative tensilestresses +σ, −σ) divided by a distance of thickness over which thechange occurs, such as a distance of 1 mm, such as a distance of 500 μm,250 μm, 100 μm (which is the distance used to quantify a rate of change,which may be a portion of article thickness, and not necessarily adimension of the article geometry). In contemplated embodiments, thedifference in peak values of the positive and negative tensile stressesis at least 50 MPa, such as at least 100 MPa, at least 150 MPa, at least200 MPa, at least 250 MPa, at least 300 MPa, at least 400 MPa, at least500 MPa, and/or no more than 5 GPa. In contemplated embodiments, theglass-based article 500 has a peak negative tensile stress of at least50 MPa in magnitude, such as at least 100 MPa, at least 150 MPa, atleast 200 MPa, at least 250 MPa, at least 300 MPa, at least 400 MPa, atleast 500 MPa. The steep tensile curve transitions generated by thesystem and method discussed herein are believed to be indicative of theability to achieve higher magnitudes of negative tensile stress at asurface of a thermally strengthened and chemically strengthenedglass-based article for a given thickness and/or to manufacture thinnerglass articles to a higher degree of negative tensile stress, such as toachieve a fragmentation potential for dicing as disclosed herein.Conventional thermal strengthening approaches may be unable to achievesuch steep tensile stress curves.

According to an exemplary embodiment, the high rate of change of tensilestress is at least one of the above-described magnitudes or greatersustained over a thickness-wise stretch of the stress profile 560 thatis at least 2% of the thickness, such as at least 5% of the thickness,at least 10% of the thickness, at least 15% of the thickness, or atleast 25% of the thickness of thermally strengthened and chemicallystrengthened glass-based article 500. In contemplated embodiments, thestrengthening extends deep into the thermally strengthened andchemically strengthened glass-based article 500 such that thethickness-wise stretch with the high rate of change of tensile stress iscentered at a depth of between 20% and 80% into the thickness from thefirst surface.

In one or more embodiments the DOC (or depth of the thermally inducedstress region) extends from a surface of the glass-based article to adepth of about 0.1●t or greater, 0.12●t or greater, 0.14●t or greater,0.15●t or greater, 0.16●t or greater, 0.17●t or greater, 0.18●t orgreater, 0.19●t or greater, 0.20●t or greater, 0.21●t or greater, 0.22●tor greater, or 0.23●t or greater. The upper limit of the DOC may beabout 0.3●t. In one or more embodiments, DOC may be measured using ascattered light polariscope (SCALP), using techniques known in the art.

In one or more embodiments, the DOL that results from chemicalstrengthening may extend from a surface of the glass-based article to anon-zero depth of up to about 0.1●t. In some embodiments, the DOL mayinclude a non-zero depth up to about 0.05●t, 0.06●t, 0.07●t, 0.08●t,0.09●t or 0.095●t. In some embodiments, the DOL may be in the range fromabout 0.001●t to about 0.1●t, from about 0.001●t to about 0.9●t, fromabout 0.001●t to about 0.8●t, from about 0.001●t to about 0.7●t, fromabout 0.001●t to about 0.6●t, from about 0.001●t to about 0.5●t, fromabout 0.001●t to about 0.4●t, from about 0.01●t to about 0.1●t, fromabout 0.015●t to about 0.1●t, from about 0.02●t to about 0.1●t, fromabout 0.03●t to about 0.1●t, from about 0.04●t to about 0.1●t, or fromabout 0.05●t to about 0.1●t.

DOL is defined as the depth to which the largest metal oxide or metalion penetrates due to chemical strengthening, as measured by microprobe,polarimetry methods such as FSM technique (described below), and thelike. In some embodiments, when chemical strengthening includes exchangeof sodium ions into the glass-based article, and thus the presence ofNa₂O at depths of up to about 0.5t, the penetration depth of sodiumcannot be readily measured by FSM technique, but can be measured bymicroprobe, SCALP, or refracted near-field (RNF) measurement (asdescribed in U.S. Pat. No. 8,854,623, entitled “Systems and methods formeasuring a profile characteristic of a glass sample”, which isincorporated herein by reference in its entirety). In some embodiments,when chemical strengthening includes exchange of potassium ions into theglass-based article, and thus the presence of K₂O, the penetration depthof potassium may be measured by FSM technique.

Compressive stress (including surface CS) is measured by surface stressmeter (FSM) using commercially available instruments such as theFSM-6000, manufactured by Orihara Industrial Co., Ltd. (Japan). Surfacestress measurements rely upon the accurate measurement of the stressoptical coefficient (SOC), which is related to the birefringence of theglass. SOC in turn is measured according to Procedure C (Glass DiscMethod) described in ASTM standard C770-16, entitled “Standard TestMethod for Measurement of Glass Stress-Optical Coefficient,” thecontents of which are incorporated herein by reference in theirentirety. Refracted near-field (RNF) method or SCALP may be used tomeasure the stress profile. When the RNF method is utilized to measurethe stress profile, the maximum CT value provided by SCALP is utilizedin the RNF method. In particular, the stress profile measured by RNF isforce balanced and calibrated to the maximum CT value provided by aSCALP measurement. The RNF method is described in U.S. Pat. No.8,854,623, entitled “Systems and methods for measuring a profilecharacteristic of a glass sample”, which is incorporated herein byreference in its entirety. In particular, the RNF method includesplacing the glass article adjacent to a reference block, generating apolarization-switched light beam that is switched between orthogonalpolarizations at a rate of between 1 Hz and 50 Hz, measuring an amountof power in the polarization-switched light beam and generating apolarization-switched reference signal, wherein the measured amounts ofpower in each of the orthogonal polarizations are within 50% of eachother. The method further includes transmitting thepolarization-switched light beam through the glass sample and referenceblock for different depths into the glass sample, then relaying thetransmitted polarization-switched light beam to a signal photodetectorusing a relay optical system, with the signal photodetector generating apolarization-switched detector signal. The method also includes dividingthe detector signal by the reference signal to form a normalizeddetector signal and determining the profile characteristic of the glasssample from the normalized detector signal. Maximum CT values aremeasured using a scattered light polariscope (SCALP) technique known inthe art.

In at least some contemplated embodiments, the thermally strengthenedand chemically strengthened glass-based article includes a change in thecomposition thereof in terms of ion content along at least a portion ofthe thickness. In one or more embodiments, the change in compositionincludes a change in the concentration of metal oxide that is bothnon-zero and varying along least a portion of the thickness, and moreparticularly, along at least a portion of the DOL or the entire DOL. Insome embodiments, the DOL is greater than the depth along which themetal oxide concentration varies. In some embodiments, the thermallystrengthened and chemically strengthened glass-based article includes afirst CS region including a concentration of metal oxide that is bothnon-zero and varies along a portion of the thickness. In someembodiments, the concentration of the metal oxide is both non-zero andvaries along the portion of the thickness from first and/or secondsurface to a depth in the range from greater than about 0●t to less thanabout 0.17●t, or in the range from greater than about 0.01●t to about0.1●t.

In one or more embodiments, the composition of the thermallystrengthened and chemically strengthened glass-based article 500 in suchembodiments includes exchanged or implanted ions that influence thestress profile 560. In some such embodiments, the exchanged or implantedions do not extend fully through the portions 530, 540 of thestrengthened thermally strengthened and chemically strengthenedglass-based article 500 because such portions are a result of thethermal strengthening as disclosed herein, instead of chemicalstrengthening. In some embodiments, the DOL extends deeper than theexchanged or implanted ions. In some embodiments, the DOL extends to adepth equal to the depth of the exchanged or implanted ions.

The stress profiles and attributes of the stress profiles of thethermally and chemically strengthened glass-based articles describedherein may be present or exhibited at the edge of the articles (i.e.,along the minor surfaces instead of the major surfaces). Referring toFIG. 6, the major surfaces 510, 520 may be masked or maintainedunexposed to the thermal or chemical strengthening process(es) so thatone or more of the minor surfaces are exposed to the thermal and/orchemical strengthening process(es). The stress profile on such minorsurfaces may be tailored for a desired performance or end use.

In one or more embodiments, the first surface 510 and the second surface520 may have stress profiles that differ from one another. For exampleany one or more of the surface CS, CS at DOL, DOL, or DOC of the firstsurface 510 may differ from that of the second surface 520. For example,in some instances, the first surface 510 requires a greater surface CSvalue than the second surface 520. In another example, the first surface510 has a greater DOC value than the DOC value of the second surface520. In some instances, such differences in any one or more of thesurface CS, CS at DOL, DOL, or DOC between the first surface 510 and thesecond surface 520 may be described as an asymmetrical stress profile.Such asymmetry may be imparted by modifying the thermal strengthening,the chemical strengthening or both the thermal and chemicalstrengthening processes used to form the glass-based articles describedherein. As will be described below, asymmetry in the stress profile mayalso be generated or enhanced by cold forming the glass-based articlesdescribed herein to a curved sheet or article.

The thermally and chemically strengthened glass-based articles describedherein may exhibit a stored tensile energy in the range from greaterthan 0 J/m² to about 40 J/m². In some instances, the stored tensileenergy may be in the range from about 5 J/m² to about 40 J/m², fromabout 10 J/m² to about 40 J/m², from about 15 J/m² to about 40 J/m²,from about 20 J/m² to about 40 J/m², from about 1 J/m² to about 35 J/m²,from about 1 J/m² to about 30 J/m², from about 1 J/m² to about 25 J/m²,from about 1 J/m² to about 20 J/m², from about 1 J/m² to about 15 J/m²,from about 1 J/m² to about 10 J/m², from about 10 J/m² to about 30 J/m²,from about 10 J/m² to about 25 J/m², from about 15 J/m² to about 30J/m², from about 15 J/m² to about 25 J/m², from about 18 J/m² to about22 J/m², from about 25 J/m² to about 40 J/m², or from about 25 J/m² toabout 30 J/m². The thermally and chemically strengthened glass-basedarticles of one or more embodiments may exhibit a stored tensile energyof about 6 J/m² or greater, about 10 J/m² or greater, about 15 J/m² orgreater, or about 20 J/m² or greater. The stored tensile energy may becalculated using the following equation: stored tensile energy(J/m²)=[(1−v)/E]∫(σ{circumflex over ( )}2) (dt), where v is Poisson'sratio, E is the Young's modulus (in MPa), σ is stress (in MPa) and theintegration is computed across the thickness (in microns) of the tensileregion only.

In various embodiments, the thermally strengthened and chemicallystrengthened glass-based article 500, have both the stress profiledescribed herein and a low, as-formed surface roughness. The processesand methods disclosed herein can thermally strengthen and chemicallystrengthen glass-based articles (which may be in sheet form) withoutincreasing the surface roughness of the as-formed surfaces. For example,incoming float glass air-side surfaces and incoming fusion formed glasssurfaces were characterized by atomic force microscopy (AFM) before andafter processing. R_(a) surface roughness was less than 1 nm (0.6-0.7nm) for incoming 1.1 mm soda-lime float glass, and the R_(a) surfaceroughness was not increased by thermal strengthening according to thepresent processes. Similarly, an R_(a) surface roughness of less than0.3 nm (0.2-0.3) for 1.1 mm sheets of fusion-formed glass was maintainedby thermal strengthening and/or chemical strengthening according to thisdisclosure. Accordingly, thermally strengthened and chemicalstrengthened glass-based articles according one or more embodiments havea surface roughness on at least a first surface in the range from 0.2 to1.5 nm R_(a) roughness, 0.2 to 0.7 nm, 0.2 to 0.4 nm or even such as 0.2to 0.3 nm, over at least an area of 10×10 μm. Surface roughness may bemeasured over an area of 10×10 μm in exemplary embodiments, or in someembodiments, 15×15 μm.

In another embodiment, the thermally strengthened and chemicallystrengthened glass-based articles described herein have high flatness.In various embodiments, the strengthening system discussed hereinutilizes controlled gas bearings to support the glass-based substrateduring transporting and heating, and in some embodiments, can be used toassist in controlling and/or improving the flatness of the resultingglass-based article, resulting in a higher degree of flatness thanpreviously obtainable, particularly for thin and/or highly strengthenedglass-based articles. For example, glass-based articles in sheet formhaving a thickness of about 0.6 mm or greater can be strengthened withimproved post-strengthening flatness. The flatness of variousembodiments of the thermally strengthened and chemically strengthenedglass-based article can comprise 100 μm or less total indicator run-out(TIR) along any 50 mm length along one of the first or second surfacesthereof, 300 μm TIR or less within a 50 mm length on one of the first orsecond surfaces, 200 μm TIR or less, 100 μm TIR or less, or 70 μm TIR orless within a 50 mm length on one of the first or second surfaces. Inexemplary embodiments, flatness is measured along any 50 mm or lessprofile of the glass-based article. In contemplated embodiments,glass-based articles, which may be in sheet form, with thicknessdisclosed herein have flatness of 200 μm TIR or less within a 20 mmlength on one of the first or second surfaces (e.g., flatness of 100 μmTIR or less, flatness 70 μm TIR or less, or flatness 50 μm TIR or less).Flatness, as used herein, was measured on a Tropel® FlatMaster® Systemavailable from Corning Incorporated (Corning, N.Y.).

According to contemplated embodiments, the thermally and chemicallystrengthened glass-based articles according to one or more embodimentshave a high-degree of dimensional consistency such that the thickness tthereof along a 1 cm lengthwise stretch of the body 522 (in FIG. 6) doesnot change by more than 50 μm, such as, by not more than 10 μm, not morethan 5 μm, not more than 2 μm. Such dimensional consistency may not beachievable for given thicknesses, areas, and/or magnitudes of negativetensile stress, as disclosed herein, by solid quenching due to practicalconsiderations, such as cooling plate alignment and/or surfaceirregularities that may distort the dimensions.

According to contemplated embodiments, the thermally and chemicallystrengthened glass-based articles according to one or more embodimentshave at least one surface (e.g., first and second surfaces 510, 520 inFIG. 6) that is flat such that a 1 cm lengthwise profile therealongstays within 50 μm of a straight line, such as within 20 μm, 10 μm, 5μm, 2 μm; and/or a 1 cm widthwise profile therealong stays within 50 μmof a straight line, such as within 20 μm, 10 μm, 5 μm, 2 μm. Such highflatness may not be achievable for given thicknesses, areas, and/ormagnitudes of negative tensile stress, as disclosed herein, by liquidquenching due to practical considerations, such as warping or bending ofthe glass strengthened in these processes due to convective currents andassociated forces of the liquid. In various embodiments, the thermallyand chemically strengthened glass-based articles according to one ormore embodiments have high fictive temperatures. It will be understoodthat in various embodiments, high fictive temperatures relate to thehigh level of thermal strengthening, high central tensile stressesand/or high compressive surface stress of the resulting glass-basedarticle 500. Surface fictive temperatures may be determined by anysuitable method, including differential scanning calorimetry, Brillouinspectroscopy, or Raman spectroscopy.

According to an exemplary embodiment, the thermally and chemicallystrengthened glass-based articles according to one or more embodimentshas a portion thereof, such as at or near the first and/or secondsurfaces 510, 520, that has a particularly high fictive temperature,such as at least 500° C., such as at least 600° C., or even at least700° C. in some embodiments. In some embodiments, the glass-basedarticle that exhibits such fictive temperatures may include a soda-limeglass. According to an exemplary embodiment, the thermally andchemically strengthened glass-based articles according to one or moreembodiments has a portion thereof, such as at or near the first and/orsecond surfaces 510, 520, that has a particularly high fictivetemperature relative to annealed glass of the same chemical composition.For example, in some embodiments, the thermally and chemicallystrengthened glass-based article exhibits a fictive temperature that isleast 10° C. greater, at least 30° C. greater, at least 50° C. greater,at least 70° C. greater, or even at least 100° C. greater than thefictive temperature of an annealed glass of the same chemicalcomposition (i.e., a glass that is and has not been thermallystrengthened according to the process described herein). High fictivetemperature may be achieved by a rapid transition from the hot to thecooling zones in the thermal strengthening system. Without being boundby theory, glass-based articles with high fictive temperature exhibitincreased damage resistance.

In some methods of determining surface fictive temperatures, it may benecessary to break the glass-based article to relieve the “temperstresses” induced by the heat strengthening process in order to measurefictive temperature with reasonably accuracy. It is well known thatcharacteristic structure bands measured by Raman spectroscopy shift in acontrolled manner both with respect to the fictive temperature and withrespect to applied stress in silicate glasses. This shift can be used tonon-destructively measure the fictive temperature if the temper stressis known.

Referring generally to FIG. 8, determination of fictive temperature forseveral exemplary glass articles is shown. Stress effects on the Ramanspectrum of silica glass are reported in D. R. Tallant, T. A. Michalske,and W. L. Smith, “The effects of tensile stress on the Raman spectrum ofsilica glass,” J. Non-Cryst. Solids, 106 380-383 (1988). Commercialglasses of 65 wt. % silica or more have substantially the same response.Although the reported stress response is for uniaxial stress, in thecase of a unibiaxial stress state such as that which is observed intempered glass, σ_(xx)=σ_(yy), the peak can be expected to shift bytwice that expected by a uniaxial stress. The peak near 1090 cm⁻¹ insoda-lime glass and in glass 2 corresponds to the 1050 cm⁻¹ peakobserved in silica glass. The effects of stress on the 1050 cm⁻¹ peak insilica, and on the corresponding peak in SLG and other silicate glassescan be expressed, as a function of stress 6 in MPa, by equation a)ω(cm⁻¹)=1054.93−0.00232·σ.

A calibration curve was produced of Raman band positions as a functionof the fictive temperature for SLG and another glass, glass 2. Glasssamples were heat-treated for various times, 2-3 times longer than thestructural relaxation times calculated by τ=10*η/G, where η is theviscosity, and G the shear modulus. After heat-treatment, the glasseswere quenched in water to freeze the fictive temperature at theheat-treatment temperature. The glass surfaces were then measured bymicro Raman at 50× magnification and a 1-2 μm spot size using a 442 nmlaser, 10-30 s exposure time, and 100% power, over the range of 200-1800cm⁻¹. The position of the peak at 1000-1200 cm⁻¹ was fit using computersoftware, Renishaw WiRE version 4.1, in this case. A good fit of the1090 cm⁻¹ Raman peak measured in SLG on the air side as a function offictive temperature Tf (in ° C.) is given by equation b)ω(cm⁻¹)=1110.66−0.0282⋅Tf. For glass 2, a good fit is given by equationc) ω(cm⁻¹)=1102.00−0.0231⋅Tf.

Using the relationships established in equations a), b), and c), it ispossible to express the fictive temperature of the glass as a functionof a measured Raman peak position with a correction factor due tosurface CS. A CS of 100 MPa, σ_(c), shifts the Raman band positionequivalent to approximately a 15 to 20 degree Celsius reduction in thefictive temperature. The following equation is applicable to SLG:

$\begin{matrix}{{T_{f}\left( {{^\circ}\mspace{14mu} {C.}} \right)} = {\left\lbrack \frac{{\omega \left( {cm}^{- 1} \right)} - {1110.66\left( {cm}^{- 1} \right)}}{{- 0.0282}\left( \frac{{cm}^{- 1}}{{^\circ}\mspace{14mu} {C.}} \right)} \right\rbrack + {2\left\lbrack {0.082*{\sigma_{c}({MPa})}} \right\rbrack}}} & (1)\end{matrix}$

The equation applicable to glass 2 is:

$\begin{matrix}{{T_{f}\left( {{^\circ}\mspace{14mu} {C.}} \right)} = {\left\lbrack \frac{{\omega \left( {cm}^{- 1} \right)} - {1102\left( {cm}^{- 1} \right)}}{{- 0.0231}\left( \frac{{cm}^{- 1}}{{^\circ}\mspace{14mu} {C.}} \right)} \right\rbrack + {2\left\lbrack {0.0996*{\sigma_{c}({MPa})}} \right\rbrack}}} & (2)\end{matrix}$

In these equations, w is the measured peak wavenumber for the peak near1090 cm⁻¹, σ_(c) is the surface CS measured by any suitable technique,yielding stress-corrected measurement of fictive temperature in ° C. Asa demonstration of increased damage resistance related to the determinedfictive temperature, four glass sheet samples were prepared, two 6 mmsoda-lime glass (SLG) sheets by conventional tempering methods toapproximately 70 and 110 MPa surface CS (CS), and two 1.1 mm SLG sheetsby the methods and systems disclosed herein to about the same levels ofCS. Two additional sheets, one of each thickness were used as controls.The surfaces of each test sheet were subjected to standard Vicker'sindentation. Various levels of force were applied, for 15 seconds each,and after a 24 hour wait, indentations were each examined. As shown inTable 1, the 50% cracking threshold (defined as the load at which theaverage number of cracks appearing is two out of the four points of theindenter at which cracks tend to initiate) was determined for eachsample.

Table 1 shows that the Vicker's crack initiation threshold for SLGprocessed by conventional convective gas tempering (as reflected in the6 mm sheet) is essentially the same as that for annealed or as-deliveredSLG sheets, rising from between zero and one newton (N) to about one toless than two newtons. This correlates with the relatively modest risein surface fictive temperature (T_(fs) or Tf_(surface)) of ˜25 to 35° C.relative to glass transition temperature (T_(g)=550° C. for SLG, definedas η=10^(12-13.3) Poise) that was provided by conventional tempering. Incontrast, by tempering using the present methods and systems, theVicker's crack initiation threshold improved to greater than 10 N, a10-fold increase over the Vicker's damage resistance imparted byconventional tempering. In the embodied glasses, the Tfs minus T_(g) wasat least 50° C., or at least 75° C., or at least 90° C., or in the rangeof from approximately 75° C. to 100° C. Even in embodiments comprisinglower levels of heat strengthening, the embodied glasses can stillprovide increased resistance, at levels such as 5 N, for instance. Incertain contemplated embodiments, the 50% cracking threshold after a 15second Vicker's crack initiation test may be equal to or greater than 5N, 10 N, 20 N, or 30 N.

TABLE 1 Cracking Thickness CS Surface T_(f) Threshold Sample (mm) (MPa)(° C.) (N) Control 1.1 Annealed ~T_(g) (550) 0-1 Control 6 Annealed~T_(g) (550) 0-1 Thin low strength 1.1 −72 626 10-20 Thick low strength6 −66 575 1-2 Thin medium strength 1.1 −106 642 10-20 Thick mediumstrength 6 −114 586 1-2

The following non-dimensional fictive temperature parameter θ can beused to compare the relative performance of a thermal strengtheningprocess in terms of the fictive temperature produced. Given in terms ofsurface fictive temperature θs in this case:

θs=(T _(fs) −T _(anneal))I(T _(soft) −T _(anneal))  (3)

where T_(fs) is the surface fictive temperature, T_(anneal) (thetemperature of the glass at a viscosity of η=10^(13.2) Poise) is theannealing point and T_(soft) (the temperature of the glass at aviscosity of η=10^(7.6) Poise) is the softening point of the glass ofthe sheet. FIG. 10 is a plot of θs for measured surface fictivetemperatures as a function of heat transfer rate, h, applied duringthermal strengthening for two different glasses. As shown in FIG. 10,the results for the two different glasses overlie each other fairlyclosely. This means that parameter θ provides a means to compare thefictive temperatures of different glasses compared directly, in relationto the heat transfer rate h required to produce them. The vertical rangeof results at each h corresponds to variation in the value of T₀, theinitial temperature at the start of quenching. In embodiments, parameterθs comprises from about (e.g., plus or minus 10%) 0.2 to about 0.9, or0.21 to 0.09, or 0.22 to 0.09, or 0.23 to 0.09, or 0.24 to 0.09, or 0.25to 0.09, or 0.30 to 0.09, or 0.40 to 0.09, or 0.5 to 0.9, or 0.51 to0.9, or 0.52 to 0.9, or 0.53 to 0.9, or 0.54 to 0.9, or 0.54 to 0.9, or0.55 to 0.9, or 0.6 to 0.9, or even 0.65 to 0.9.

At higher thermal transfer rates (such as at about 800 W/m²K and above,for example), however, the high temperature or “liquidus” CTE of theglass begins to affect tempering performance. Therefore, under suchconditions, the temperability parameter V, based on an approximation ofintegration over the changing CTE values across the viscosity curve, isfound to be useful:

Ψ=E·[T _(strain)·α_(CTE) ^(S)+α_(CTE) ^(L)·(T _(soft) −T_(strain))]  (5)

where α^(S) _(CTE) is the low temperature linear CTE (equivalent to theaverage linear expansion coefficient from 0-300° C. for the glass),expressed in 1/° C. (° C.⁻¹), α^(L) _(CTE) is the high temperaturelinear CTE (equivalent to the high-temperature plateau value which isobserved to occur somewhere between the glass transition and softeningpoint), expressed in 1/° C. (° C.⁻¹), E is the elastic modulus of theglass, expressed in GPa (not MPa) (which allows values of the(non-dimensional) parameter Ψ to range generally between 0 and 1),T_(strain) is the strain point temperature of the glass, (thetemperature of the glass at a viscosity of η=10^(14.7) Poise) expressedin ° C., and T_(soft) is the softening point of the glass (thetemperature of the glass at a viscosity of η=10^(7.6) Poise), expressedin ° C.

The thermal strengthening process and resulting surface CS values weremodeled for glasses having varying properties to determine the temperingparameter, Ψ. The glasses were modeled at the same starting viscosity of10^(8.2) Poise and at varying heat transfer coefficients. The propertiesof the various glasses are shown in Table 2, together with thetemperature for each glass at 10^(8.2) Poise and the calculated value ofthe temperability parameter Ψ for each.

TABLE 2 10^(8.2) Softening Strain CTE CTE Poise Point Point GlassModulus low high ° C. ° C. ° C. Ψ SLG 72 8.8 27.61 705 728 507 0.76 273.3 8.53 20.49 813 837 553 0.77 3 65.5 8.26 26 821 862 549 0.83 4 658.69 20.2 864 912 608 0.74 5 63.9 10.61 22 849 884 557 0.84 6 58.26 3.520.2 842 876 557 0.49 7 73.6 3.6 13.3 929 963 708 0.44 8 81.1 3.86 12.13968 995 749 0.48

The results in Table 2 show that Ψ is proportional to the thermalstrengthening performance of the glass. This correlation is furthershown in FIG. 9, which provides an embodied example for a high heattransfer rate (a heat transfer coefficient of 2093 W/m²K (0.05cal/s·cm²·° C.)) and a glass sheet thickness of only 1 mm. As seen inthe figure, the variation in the seven differing glasses' resulting CScorrelates well with the variation in the proposed temperabilityparameter Ψ.

In another aspect, it has been found that for any glass, at any givenvalue of the heat transfer coefficient, h (expressed in cal/cm²-s-° C.),the curves of surface CS (σ_(CS), in MPa) vs. thickness (t, in mm) canbe fit (over the range of t from 0 to 6 mm) by the hyperbola, where P₁and P₂ are functions of h such that:

$\begin{matrix}{\begin{matrix}{{\sigma_{CS}\left( {{Glass},h,t} \right)} = {{C\left( {h,t} \right)}*{\Psi ({Glass})}}} \\{= {\frac{{P_{1}(h)}*t}{\left( {{P_{2}(h)} + t} \right)}*{\Psi ({Glass})}}}\end{matrix}\quad} & (6)\end{matrix}$

or with the expression for substituted in, the curve of CS σ_(CS)(Glass,h, t) is given by:

$\begin{matrix}{\frac{{P_{1}(h)}*t}{\left( {{P_{2}(h)} + t} \right)} \cdot E \cdot \left\lbrack {{T_{strain} \cdot \alpha_{CTE}^{s}} + {\alpha_{CTE}^{L} \cdot \left( {T_{soft} - T_{strain}} \right)}} \right\rbrack} & (7)\end{matrix}$

where the constants P₁, P₂, in either (6) or (7) above, are eachcontinuous functions of the heat transfer value, h, given by:

$\begin{matrix}{{P_{1} = {910.2 - {259.2 \cdot {\exp \left( {- \frac{h}{0.143}} \right)}}}}{and}} & (8) \\{P_{2} = {2.53 + \frac{23.65}{\left( {1 + \left( \frac{h}{0.00738} \right)^{1.58}} \right)}}} & (9)\end{matrix}$

The constants P₁, P₂, are graphed as functions of h in FIGS. 10 and 11,respectively. Accordingly, by using a value of P₁, for a given h and thecorresponding P₂, for that same h in expression (6) or (7) above, acurve is specified corresponding to the surface CS (CS) obtainable atthat h, as a function of thickness t.

In some embodiments, a similar expression may be used to predict the CTof a thermally strengthened glass sheet, particularly at a thickness of6 mm and less, and the thermal transfer coefficient, such as 800 W/m²Kand up, by simply dividing the CS predicted under the same conductionsby 2. Thus, expected CT may be given by

$\begin{matrix}{\frac{{P_{1{CT}}\left( h_{CT} \right)}*t}{\left( {{P_{2{CT}}\left( h_{CT} \right)} + t} \right)} \cdot E \cdot \left\lbrack {{T_{strain} \cdot \alpha_{CTE}^{s}} + {\alpha_{CTE}^{L} \cdot \left( {T_{soft} - T_{strain}} \right)}} \right\rbrack} & (10)\end{matrix}$

Where P_(1CT) and P_(2CT) are given as follows:

$\begin{matrix}{{P_{1{CT}} = {910.2 - {259.2 \cdot {\exp \left( {- \frac{h_{CT}}{0.143}} \right)}}}}{and}} & (11) \\{P_{2{CT}} = {2.53 + \frac{23.65}{\left( {1 + \left( \frac{h_{CT}}{0.00738} \right)^{1.58}} \right)}}} & (12)\end{matrix}$

In some embodiments, h and h_(CT), may have the same value for a givenphysical instance of thermal strengthening. However, in someembodiments, they may vary, and providing separate variables andallowing variation between them allows for capturing, within descriptiveperformance curves, instances in which the typical ratio of 2:1 CS/CTdoes not hold.

One or more embodiments of the currently disclosed processes and systemshave produced thermally strengthened SLG sheets at all of the heattransfer rate values (h and h_(CT)) shown in Table 3.

TABLE 3 h and h_(CT) values according to exemplary embodiments cal/s ·cm² · ° C. W/m²K 0.010 418.68 0.013 544.284 0.018 753.624 0.019 795.4920.020 837.36 0.021 879.228 0.022 921.096 0.023 962.964 0.027 1130.4360.028 1172.304 0.029 1214.172 0.030 1256.04 0.031 1297.908 0.0331381.644 0.034 1423.512 0.038 1590.984 0.040 1674.72 0.041 1716.5880.042 1758.456 0.045 1884.06 0.047 1967.796 0.048 2009.664 0.0492051.532 0.050 2093.4 0.051 2135.268 0.052 2177.136 0.053 2219.004 0.0542260.872 0.055 2302.74 0.060 2512.08 0.061 2553.948 0.062 2595.816 0.0632637.684 0.065 2721.42 0.067 2805.156 0.069 2888.892 0.070 2930.76 0.0712972.628 0.078 3265.704 0.080 3349.44 0.081 3391.308 0.082 3433.1760.095 3977.46 0.096 4019.328 0.102 4270.536 0.104 4354.272 0.105 4396.140.127 5317.236 0.144 6028.992 0.148 6196.464 0.149 6238.332 0.1847703.712

In some embodiments, the heat transfer value rates (h and h_(CT)) may befrom about 0.024 to about 0.15, about 0.026 to about 0.10, or about0.026 to about 0.075 cal/s·cm²·° C.

FIG. 12 shows the newly opened performance space in MPa of surfacecompression of a glass sheet as a function of thickness t (in mm), by agraph of C(h,t)·Ψ(SLG) for selected values of h according to equations6-9 above, with Ψ(SLG) corresponding to the value of Ψ for SLG in Table2. The traces labeled GC represent the estimated range of maximumstresses versus thinness of SLG sheets achievable by gas convectivetempering, from 0.02 cal/s·cm²·° C. (or 840 W/m²K) to 0.03 cal/s·cm²·°C. or 1250 W/m²K, assuming that these levels of heat transfercoefficient can be employed in that process at a heated glass viscosityof 10^(8.2) Poises or about 704° C., a temperature above the capabilityof convective gas processes.

Examples of highest reported sheet CS values based on gas convectivetempering processes are shown by the triangle markers labeled Gas in thelegend. The value 601 represents advertised product performancecapability of commercial equipment, while the value 602 is based on anoral report at a glass processing conference. The trace labeled LCrepresents the curve of maximum stresses versus thinness of SLG sheetsestimated to be achievable by liquid contact tempering, given by a heattransfer rate h of 0.0625 cal/s·cm²·° C. (or about 2600 W/m²K), alsoassuming processing at an initial heated glass viscosity of 10^(8.2)Poises or about 704° C. Examples of highest reported sheet CS valuesbased on liquid contact tempering processes are shown by the circlemarkers labeled Liquid in the legend. The higher of the two values at 2mm thickness is based on a report of tempering of a borosilicate glasssheet, and the stress achieved has been scaled for the figure by(Ψ_(SLG))/(Ψ_(borosilicate)) for scaled direct comparison.

The trace labeled 704 represents stresses achievable by one or moreembodiments of the presently disclosed methods and systems at a heattransfer rate of 0.20 cal/s·cm²·° C. (or about 8370 W/m²K) and aninitial temperature, just before quenching, of 704° C. The level ofstress on the glass sheet thus achievable represents almost the samescope of improvement over liquid tempering strength levels as liquidtempering represents over state of the art gas convective tempering. Butthe trace labeled 704 is not an upper limit—embodiments have been shownto be viable above this value due to the good control of form andflatness achievable in a small-gap gas bearing thermal strengthening ateven higher temperatures (at lower viscosities of the glass). The tracelabeled 730 shows some of the additional strengthening performanceachieved by a heat transfer rate of 0.20 cal/s·cm²·° C. (or about 8370W/m²K) at a starting temperature for a SLG sheet of 730° C., very nearor above the softening point of the glass. Significant improvements inCS and thus in glass sheet strength are thus achieved particularly bythe combination of high heat transfer rate and the use of high initialtemperatures enabled by the good handling and control of sheet flatnessand form in a tight gas bearing—and the improvements are particularlystriking at thickness 2 mm and below.

FIG. 13 shows the traces of FIG. 12 explained above, at 2 mm and below,but with CS as a function of thickness plotted for selected examples ofthermally strengthened glass-based articles by one or more embodimentsof the present disclosure, showing the extreme combination of thermalstrengthening levels and thinness enabled by the present disclosure.

In one or more embodiments, the thermally strengthened and chemicallystrengthened glass-based article includes a low coefficient of thermalexpansion (CTE) glass. As discussed above (see e.g., equations 7 and10), thermal strengthening effects are significantly dependent upon theCTE of the glass of which the glass sheet is comprised. However, thermalstrengthening of low CTE glasses may provide strengthened glasscompositions having advantageous properties, such as increased chemicalresistance, or better compatibility with electronic devices due to lowalkali content. Glass having CTEs of 65, 60, 55, 50, 45, 40, and even35×10⁻⁶° C.⁻¹ and below are capable of safety-glass like break patterns(“dicing”) at thicknesses of less than 4 mm, less than 3.5 mm, less than3 mm, and even at 2 mm or less. Glasses having CTE values of 40×10⁻⁶°C.⁻¹ and below can be strengthened using the processes described herein.

In one or more embodiments, the thermally strengthened and chemicallystrengthened glass-based article includes a glass composition havingmoderate to high CTE values. Example glasses include alkalialuminosilicates, boroaluminosilicates, and soda-lime glasses. In someembodiments, the glasses having CTEs greater than 40, greater than 50,greater than 60, greater than 70, greater than 80, or greater than90×10⁻⁷/° C. maybe thermally and chemically strengthened as describedherein. Some such CTEs may be particularly low for thermal tempering asdisclosed herein, where the degree of negative tensile stress is no morethan 50 MPa and/or at least 10 MPa.

In one or more embodiments, the thermally strengthened and chemicallystrengthened glass-based article exhibits superior performance asmeasured by a Knoop scratch threshold test and/or a Vicker's crackinitiation threshold test. For example, in one or more embodiments, thethermally strengthened and chemically strengthened glass-based articleexhibits a Knoop scratch threshold (as measured by the Knoop scratchthreshold test) of about 8 N or greater (e.g., 9 N or greater, 10 N orgreater, 11 N or greater, 12 N or greater, 13 N or greater or 14 N orgreater). In some instances the upper limit of the Knoop scratchthreshold may be about 20 N. In one or more embodiments, the thermallystrengthened and chemically strengthened glass-based article exhibits aVicker's crack initiation threshold (as measured by the Vicker's crackinitiation threshold test) of about 120 N or greater. For example, theVicker's crack initiation threshold may be about 125 N or greater, 130 Nor greater, 135 N or greater, 140 N or greater, 145 N or greater, 150 Nor greater, 155 N or greater or about 160 N or greater. The upper limitof the Vicker's crack initiation threshold may be about 180 N.

In some applications and embodiments, the thermally strengthened andchemically strengthened glass-based articles may have a compositionconfigured for chemical durability. In some such embodiments, thecomposition comprises at least 70% silicon dioxide by weight, and/or atleast 10% sodium oxide by weight, and/or at least 7% calcium oxide byweight. Conventional articles of such compositions may be difficult tochemically temper to a deep depth, and/or may be difficult, if notimpossible, to thermally temper by conventional processes to asufficient magnitude of negative surface tensile stress for thinthicknesses, such as due to fragility and forces of conventionalprocesses.

In some contemplated embodiments, glass-based substrates strengthenedvia the processes and systems discussed herein (such as glass sheet 500)may include an amorphous substrate, a crystalline substrate or acombination thereof, such as a glass-ceramic substrate. Glass-basedsubstrates strengthened via the processes and systems discussed hereinmay include an alkali aluminosilicate glass, alkali containingborosilicate glass, alkali aluminophosphosilicate glass or alkalialuminoborosilicate glass. In one or more embodiments, glass-basedsubstrates may include a glass having a composition, in mole percent(mol %), including: SiO₂ in the range from about (e.g., plus or minus1%) 40 to about 80 mol %, Al₂O₃ in the range from about 10 to about 30mol %, B₂O₃ in the range from about 0 to about 10 mol %, R₂O in therange from about 0 to about 20 mol %, and/or RO in the range from about0 to about 15 mol %. In some contemplated embodiments, the compositionmay include either one or both of ZrO₂ in the range from about 0 toabout 5 mol % and P₂O₅ in the range from about 0 to about 15 mol %. Insome contemplated embodiments, TiO₂ can be present from about 0 to about2 mol %.

In one or more embodiments, the glass-based article or substrate (priorto being chemically strengthened as described herein) may include aglass composition, in mole percent (mole %), including:

SiO₂ in the range from about 40 to about 80, Al₂O₃ in the range fromabout 10 to about 30, B₂O₃ in the range from about 0 to about 10, R₂O inthe range from about 0 to about 20, and RO in the range from about 0 toabout 15. As used herein, R₂O refers to alkali metal oxides such asLi₂O, Na₂O, K₂O, Rb₂O, and Cs₂O. As used herein RO refers to MgO, CaO,SrO, BaO, ZnO and the like. In some instances, the composition mayinclude either one or both of ZrO₂ in the range from about 0 mol % toabout 5 mol % and P₂O₅ in the range from about 0 to about 15 mol %. TiO₂can be present from about 0 mol % to about 2 mol %.

In some embodiments, the glass composition may include SiO₂ in anamount, in mol %, in the range from about 45 to about 80, from about 45to about 75, from about 45 to about 70, from about 45 to about 65, fromabout 45 to about 60, from about 45 to about 65, from about 45 to about65, from about 50 to about 70, from about 55 to about 70, from about 60to about 70, from about 70 to about 75, from about 70 to about 72, fromabout 50 to about 65, or from about 60 to about 65.

In some embodiments, the glass composition may include Al₂O₃ in anamount, in mol %, in the range from about 5 to about 28, from about 5 toabout 26, from about 5 to about 25, from about 5 to about 24, from about5 to about 22, from about 5 to about 20, from about 6 to about 30, fromabout 8 to about 30, from about 10 to about 30, from about 12 to about30, from about 14 to about 30, 15 to about 30, or from about 12 to about18.

In one or more embodiments, the glass composition may include B₂O₃ in anamount, in mol %, in the range from about 0 to about 8, from about 0 toabout 6, from about 0 to about 4, from about 0.1 to about 8, from about0.1 to about 6, from about 0.1 to about 4, from about 1 to about 10,from about 2 to about 10, from about 4 to about 10, from about 2 toabout 8, from about 0.1 to about 5, or from about 1 to about 3. In someinstances, the glass composition may be substantially free of B₂O₃. Asused herein, the phrase “substantially free” with respect to thecomponents of the glass composition means that the component is notactively or intentionally added to the glass compositions during initialbatching or subsequent ion exchange, but may be present as an impurity.For example, a glass may be describe as being substantially free of acomponent, when the component is present in an amount of less than about0.1001 mol %. Without being bound by theory, the addition of boronincreases the high temperature coefficient of thermal expansion of theglass composition, which can result in a thermally and chemicallystrengthened glass-based article that exhibits a greater CT value, afterthermal strengthening. In some embodiments, this higher CT value issubstantially maintained or even increased after chemical strengthening.

In some embodiments, the glass composition may include one or morealkali earth metal oxides, such as MgO, CaO and ZnO. In someembodiments, the total amount of the one or more alkali earth metaloxides may be a non-zero amount up to about 15 mol %. In one or morespecific embodiments, the total amount of any of the alkali earth metaloxides may be a non-zero amount up to about 14 mol %, up to about 12 mol%, up to about 10 mol %, up to about 8 mol %, up to about 6 mol %, up toabout 4 mol %, up to about 2 mol %, or up about 1.5 mol %. In someembodiments, the total amount, in mol %, of the one or more alkali earthmetal oxides may be in the range from about 0.01 to 10, from about 0.01to 8, from about 0.01 to 6, from about 0.01 to 5, from about 0.05 to 10,from about 0.05 to 2, or from about 0.05 to 1. The amount of MgO may bein the range from about 0 mol % to about 5 mol % (e.g., from about 0.001to about 1, from about 0.01 to about 2, or from about 2 mol % to about 4mol %). The amount of ZnO may be in the range from about 0 to about 2mol % (e.g., from about 1 mol % to about 2 mol %). The amount of CaO maybe from about 0 mol % to about 2 mol %. In one or more embodiments, theglass composition may include MgO and may be substantially free of CaOand ZnO. In one variant, the glass composition may include any one ofCaO or ZnO and may be substantially free of the others of MgO, CaO andZnO. In one or more specific embodiments, the glass composition mayinclude only two of the alkali earth metal oxides of MgO, CaO and ZnOand may be substantially free of the third of the earth metal oxides.

The total amount, in mol %, of alkali metal oxides R₂O in the glasscomposition may be in the range from about 5 to about 20, from about 5to about 18, from about 5 to about 16, from about 5 to about 15, fromabout 5 to about 14, from about 5 to about 12, from about 5 to about 10,from about 5 to about 8, from about 5 to about 20, from about 6 to about20, from about 7 to about 20, from about 8 to about 20, from about 9 toabout 20, from about 10 to about 20, from about 11 to about 20, fromabout 12 to about 18, or from about 14 to about 18.

In one or more embodiments, the glass composition includes Na₂O in anamount in the range from about 0 mol % to about 18 mol %, from about 0mol % to about 16 mol % or from about 0 mol % to about 14 mol %, fromabout 0 mol % to about 12 mol %, from about 2 mol % to about 18 mol %,from about 4 mol % to about 18 mol %, from about 6 mol % to about 18 mol%, from about 8 mol % to about 18 mol %, from about 8 mol % to about 14mol %, from about 8 mol % to about 12 mol %, or from about 10 mol % toabout 12 mol %. In some embodiments, the composition may include atleast about 4 mol % Na₂O. In some embodiments, the composition mayinclude less than about 4 mol % Na₂O.

In some embodiments, the amount of Li₂O and Na₂O is controlled to aspecific amount or ratio to balance formability and ion exchangeability.For example, as the amount of Li₂O increases, the liquidus viscosity maybe reduced, thus preventing some forming methods from being used;however, such glass compositions are ion exchanged to deeper DOC levels,as described herein. The amount of Na₂O can modify liquidus viscositybut can inhibit ion exchange to deeper DOC levels.

In one or more embodiments, the glass composition may include K₂O in anamount less than about 5 mol %, less than about 4 mol %, less than about3 mol %, less than about 2 mol %, or less than about 1 mol %. In one ormore alternative embodiments, the glass composition may be substantiallyfree, as defined herein, of K₂O.

In one or more embodiments, the glass composition may include Li₂O in anamount about 0 mol % to about 18 mol %, from about 0 mol % to about 15mol % or from about 0 mol % to about 10 mol %, from about 0 mol % toabout 8 mol %, from about 0 mol % to about 6 mol %, from about 0 mol %to about 4 mol % or from about 0 mol % to about 2 mol %. In someembodiments, the glass composition may include Li₂O in an amount about 2mol % to about 10 mol %, from about 4 mol % to about 10 mol %, fromabout 6 mol % to about 10 mol, or from about 5 mol % to about 8 mol %.In one or more alternative embodiments, the glass composition may besubstantially free, as defined herein, of Li₂O.

In one or more embodiments, the glass composition may include Fe₂O₃. Insuch embodiments, Fe₂O₃ may be present in an amount less than about 1mol %, less than about 0.9 mol %, less than about 0.8 mol %, less thanabout 0.7 mol %, less than about 0.6 mol %, less than about 0.5 mol %,less than about 0.4 mol %, less than about 0.3 mol %, less than about0.2 mol %, less than about 0.1 mol % and all ranges and sub-rangestherebetween. In one or more alternative embodiments, the glasscomposition may be substantially free, as defined herein, of Fe₂O₃.

In one or more embodiments, the glass composition may include ZrO₂. Insuch embodiments, ZrO₂ may be present in an amount less than about 1 mol%, less than about 0.9 mol %, less than about 0.8 mol %, less than about0.7 mol %, less than about 0.6 mol %, less than about 0.5 mol %, lessthan about 0.4 mol %, less than about 0.3 mol %, less than about 0.2 mol%, less than about 0.1 mol % and all ranges and sub-ranges therebetween.In one or more alternative embodiments, the glass composition may besubstantially free, as defined herein, of ZrO₂.

In one or more embodiments, the glass composition may include P₂O₅ in arange from about 0 mol % to about 10 mol %, from about 0 mol % to about8 mol %, from about 0 mol % to about 6 mol %, from about 0 mol % toabout 4 mol %, from about 0.1 mol % to about 10 mol %, from about 0.1mol % to about 8 mol %, from about 2 mol % to about 8 mol %, from about2 mol % to about 6 mol % or from about 2 mol % to about 4 mol %. In someinstances, the glass composition may be substantially free of P₂O₅.

In one or more embodiments, the glass composition may include TiO₂. Insuch embodiments, TiO₂ may be present in an amount less than about 6 mol%, less than about 4 mol %, less than about 2 mol %, or less than about1 mol %. In one or more alternative embodiments, the glass compositionmay be substantially free, as defined herein, of TiO₂. In someembodiments, TiO₂ is present in an amount in the range from about 0.1mol % to about 6 mol %, or from about 0.1 mol % to about 4 mol %.

In some embodiments, glass composition may be substantially free ofnucleating agents. Examples of typical nucleating agents are TiO₂, ZrO₂and the like. Nucleating agents may be described in terms of function inthat nucleating agents are constituents in the glass can initiate theformation of crystallites in the glass.

In some contemplated embodiments, compositions used for the glass-basedsubstrates or articles discussed herein may be batched with 0-2 mol % ofat least one fining agent selected from any one or more of Na₂SO₄, NaCl,NaF, NaBr, K₂SO₄, KCl, KF, KBr, As₂O₃, Sb₂O₃, and SnO₂. The glasscomposition according to one or more embodiments may further includeSnO₂ in the range from about 0 to about 2 mol %, from about 0 to about 1mol %, from about 0.1 to about 2 mol %, from about 0.1 to about 1 mol %,or from about 1 to about 2 mol %. Glass compositions disclosed hereinfor the glass-based substrates or articles may be substantially free ofAs₂O₃ and/or Sb₂O₃, in some embodiments.

In one or more embodiments, the composition of the glass-basedsubstrates or articles described herein may specifically include fromabout 62 mol % to 75 mol % SiO₂; from about 10.5 mol % to about 17 mol %Al₂O₃; from about 5 mol % to about 13 mol % Li₂O; from about 0 mol % toabout 4 mol % ZnO; from about 0 mol % to about 8 mol % MgO; from about 2mol % to about 5 mol % TiO₂; from about 0 mol % to about 4 mol % B₂O₃;from about 0 mol % to about 5 mol % Na₂O; from about 0 mol % to about 4mol % K₂O; from about 0 mol % to about 2 mol % ZrO₂; from about 0 mol %to about 7 mol % P₂O₅; from about 0 mol % to about 0.3 mol % Fe₂O₃; fromabout 0 mol % to about 2 mol % MnOx; and from about 0.05 mol % to about0.2 mol % SnO₂.

In one or more embodiments, the composition of the glass-basedsubstrates or articles described herein may include from about 67 mol %to about 74 mol % SiO₂; from about 11 mol % to about 15 mol % Al₂O₃;from about 5.5 mol % to about 9 mol % Li₂O; from about 0.5 mol % toabout 2 mol % ZnO; from about 2 mol % to about 4.5 mol % MgO; from about3 mol % to about 4.5 mol % TiO₂; from about 0 mol % to about 2.2 mol %B₂O₃; from about 0 mol % to about 1 mol % Na₂O; from about 0 mol % toabout 1 mol % K₂O; from about 0 mol % to about 1 mol % ZrO₂; from about0 mol % to about 4 mol % P₂O₅; from about 0 mol % to about 0.1 mol %Fe₂O₃; from about 0 mol % to about 1.5 mol % MnOx; and from about 0.08mol % to about 0.16 mol % SnO₂.

In one or more embodiments, the composition of the glass-basedsubstrates or articles described herein may include from about 70 mol %to 75 mol % SiO₂; from about 10 mol % to about 15 mol % Al₂O₃; fromabout 5 mol % to about 13 mol % Li₂O; from about 0 mol % to about 4 mol% ZnO; from about 0.1 mol % to about 8 mol % MgO; from about 0 mol % toabout 5 mol % TiO₂; from about 0.1 mol % to about 4 mol % B₂O₃; fromabout 0.1 mol % to about 5 mol % Na₂O; from about 0 mol % to about 4 mol% K₂O; from about 0 mol % to about 2 mol % ZrO₂; from about 0 mol % toabout 7 mol % P₂O₅; from about 0 mol % to about 0.3 mol % Fe₂O₃; fromabout 0 mol % to about 2 mol % MnOx; and from about 0.05 mol % to about0.2 mol % SnO₂.

In one or more embodiments, the composition of the glass-basedsubstrates or articles described herein may include from about 52 mol %to about 65 mol % SiO₂; from about 14 mol % to about 18 mol % Al₂O₃;from about 5.5 mol % to about 7 mol % Li₂O; from about 1 mol % to about2 mol % ZnO; from about 0.01 mol % to about 2 mol % MgO; from about 4mol % to about 12 mol % Na₂O; from about 0.1 mol % to about 4 mol %P₂O₅; and from about 0.01 mol % to about 0.16 mol % SnO₂. In someembodiments, the composition may be substantially free of any one ormore of B₂O₃, TiO₂, K₂O and ZrO₂.

In one or more embodiments, the composition of the glass-basedsubstrates or articles described herein may include at least 0.5 mol %P₂O₅, Na₂O and, optionally, Li₂O, where Li₂O (mol %)/Na₂O (mol %)<1. Inaddition, these compositions may be substantially free of B₂O₃ and K₂O.In some embodiments, the composition may include ZnO, MgO, and SnO₂.

In some embodiments, the composition of the glass-based substrates orarticles described herein may comprise: from about 58 mol % to about 65mol % SiO₂; from about 11 mol % to about 19 mol % Al₂O₃; from about 0.5mol % to about 3 mol % P₂O₅; from about 6 mol % to about 18 mol % Na₂O;from 0 mol % to about 6 mol % MgO; and from 0 mol % to about 6 mol %ZnO. In certain embodiments, the composition may comprise from about 63mol % to about 65 mol % SiO₂; from 11 mol % to about 17 mol % Al₂O₃;from about 1 mol % to about 3 mol % P₂O₅; from about 9 mol % to about 20mol % Na₂O; from 0 mol % to about 6 mol % MgO; and from 0 mol % to about6 mol % ZnO.

In some embodiments, the composition of the glass-based substrates orarticles described herein may include the following compositionalrelationships R₂O (mol %)/Al₂O₃ (mol %)<2, where R₂O=Li₂O+Na₂O. In someembodiments, 65 mol %<SiO₂ (mol %)+P₂O₅ (mol %)<67 mol %. In certainembodiments, R₂O (mol %)+R′O (mol %)−Al₂O₃ (mol %)+P₂O₅ (mol %)>−3 mol%, where R₂O=Li₂O+Na₂O and R′O is the total amount of divalent metaloxides present in the composition.

In contemplated embodiments, the glass-based substrates or articles mayinclude alkali aluminosilicate glass compositions or alkalialuminoborosilicate glass compositions. One example glass compositioncomprises SiO₂, B₂O₃ and Na₂O, where (SiO₂+B₂O₃)≥66 mol. %, and/orNa₂O≥9 mol. %. In an embodiment, the glass composition includes at least6 wt. % aluminum oxide. In a further embodiment, the glass-basedsubstrates or articles discussed herein may include a glass compositionwith one or more alkaline earth oxides, such that a content of alkalineearth oxides is at least 5 wt. %. Suitable glass compositions, in someembodiments, further comprise at least one of K₂O, MgO and CaO. In aparticular embodiment, the glass compositions used in the strengthenedglass or glass-ceramic sheet or article discussed herein can comprise61-75 mol. % SiO₂; 7-15 mol. % Al₂O₃; 0-12 mol. % B₂O₃; 9-21 mol. %Na₂O; 0-4 mol. % K₂O; 0-7 mol. % MgO; and/or 0-3 mol. % CaO.

A further example glass composition suitable for the glass-basedsubstrates or articles discussed herein comprises: 60-70 mol. % SiO₂;6-14 mol. % Al₂O₃; 0-15 mol. % B₂O₃; 0-15 mol. % Li₂O; 0-20 mol. % Na₂O;0-10 mol. % K₂O; 0-8 mol. % MgO; 0-10 mol. % CaO; 0-5 mol. % ZrO₂; 0-1mol. % SnO₂; 0-1 mol. % CeO₂; less than 50 ppm As₂O₃; and less than 50ppm Sb₂O₃; where 12 mol. %≤(Li₂O+Na₂O+K₂O)≤20 mol. % and/or 0 mol.%≤(MgO+CaO)≤10 mol. %. A still further example glass compositionsuitable for the glass-based substrates or articles discussed hereincomprises: 63.5-66.5 mol. % SiO₂; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃;0-5 mol. % Li₂O; 8-18 mol. % Na₂O; 0-5 mol. % K₂O; 1-7 mol. % MgO; 0-2.5mol. % CaO; 0-3 mol. % ZrO₂; 0.05-0.25 mol. % SnO₂; 0.05-0.5 mol. %CeO₂; less than 50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 14 mol.%≤(Li₂O+Na₂O+K₂O)≤18 mol. % and/or 2 mol. % (MgO+CaO) 7 mol. %.

In particular contemplated embodiments, an alkali aluminosilicate glasscomposition suitable for the glass-based substrates or articlesdiscussed herein comprises alumina, at least one alkali metal and, insome embodiments, greater than 50 mol. % SiO₂, in other embodiments atleast 58 mol. % SiO₂, and in still other embodiments at least 60 mol. %SiO₂, wherein the ratio (Al₂O₃+B₂O₃)/Σmodifiers (i.e., sum of modifiers)is greater than 1, where in the ratio the components are expressed inmol. % and the modifiers are alkali metal oxides. This glasscomposition, in particular embodiments, comprises: 58-72 mol. % SiO₂;9-17 mol. % Al₂O₃; 2-12 mol. % B₂O₃; 8-16 mol. % Na₂O; and/or 0-4 mol. %K₂O, wherein the ratio (Al₂O₃+B₂O₃)/Σmodifiers (i.e., sum of modifiers)is greater than 1. In still another embodiment, the glass-basedsubstrates or articles may include an alkali aluminosilicate glasscomposition comprising: 64-68 mol. % SiO₂; 12-16 mol. % Na₂O; 8-12 mol.% Al₂O₃; 0-3 mol. % B₂O₃; 2-5 mol. % K₂O; 4-6 mol. % MgO; and 0-5 mol. %CaO, wherein: 66 mol. % SiO₂+B₂O₃+CaO≤69 mol. %;Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>10 mol. %; 5 mol. %≤MgO+CaO+SrO≤8 mol. %;(Na₂O+B₂O₃)−Al₂O₃≤2 mol. %; 2 mol. % Na₂O−Al₂O₃ 6≤mol. %; and 4 mol. %(Na₂O+K₂O)−Al₂O₃≤10 mol. %. In an alternative embodiment, theglass-based substrates or articles discussed herein may comprise analkali aluminosilicate glass composition comprising: 2 mol. % or more ofAl₂O₃ and/or ZrO₂, or 4 mol. % or more of Al₂O₃ and/or ZrO₂.

In one or more embodiments, the glass substrates may exhibit a strainpoint of about 500° C. or greater. For example, the strain point may beabout 550° C. or greater, about 600° C. or greater, or about 650° C. orgreater.

In contemplated embodiments, examples of suitable glass ceramics for theglass-based substrates or articles discussed herein may includeLi₂O—Al₂O₃—SiO₂ system (i.e. LAS-System) glass ceramics, MgO—Al₂O₃—SiO₂system (i.e. MAS-System) glass ceramics, and/or glass ceramics thatinclude a predominant crystal phase including β-quartz solid solution,β-spodumene ss, cordierite, and lithium disilicate. The glass-basedsubstrates or articles discussed herein may be characterized by themanner in which it is formed. For instance, the strengthened glass orglass-ceramic sheet or article discussed herein may be characterized asfloat-formable (i.e., formed by a float process), down-drawable and, inparticular, fusion-formable or slot-drawable (i.e., formed by a downdraw process such as a fusion draw process or a slot draw process).

A float-formable glass-based substrates or articles may be characterizedby smooth surfaces and consistent thickness, and is made by floatingmolten glass on a bed of molten metal, typically tin. In an exampleprocess, molten glass that is fed onto the surface of the molten tin bedforms a floating glass or glass-ceramic ribbon. As the glass ribbonflows along the tin bath, the temperature is gradually decreased untilthe glass ribbon solidifies into a solid glass-based that can be liftedfrom the tin onto rollers. Once off the bath, the glass-based substratecan be cooled further and annealed to reduce internal stress. Where theglass-based article is a glass ceramic, the glass substrate formed fromthe float process may be subjected to a ceramming process by which oneor more crystalline phases are generated.

Down-draw processes produce glass-based substrates having a consistentthickness that possess relatively pristine surfaces. Because the averageflexural strength of the glass-based substrates is controlled by theamount and size of surface flaws, a pristine surface that has hadminimal contact has a higher initial strength. When this high strengthglass-based substrates is then further strengthened as described herein,the resultant strength can be higher than that of a glass-basedsubstrate with a surface that has been lapped and polished. Down-drawnglass-based substrates may be drawn to a thickness of less than about 2mm (for example 1.5 mm, 1 mm, 0.75 mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm,0.2 mm, 0.1 mm, 0.075 mm, 0.050 mm). In addition, down-drawn glass-basedsubstrates have a very flat, smooth surface that can be used in itsfinal application without costly grinding and polishing. Where theglass-based substrates is a glass ceramic, the glass-based substratesformed from the down-draw process may be subjected to a cerammingprocess by which one or more crystalline phases are generated.

The fusion draw process, for example, uses a drawing tank that has achannel for accepting molten glass raw material. The channel has weirsthat are open at the top along the length of the channel on both sidesof the channel. When the channel fills with molten material, the moltenglass overflows the weirs. Due to gravity, the molten glass flows downthe outside surfaces of the drawing tank as two flowing glass films.These outside surfaces of the drawing tank extend down and inwardly sothat they join at an edge below the drawing tank. The two flowing glassfilms join at this edge to fuse and form a single flowing glass article.The fusion draw method offers the advantage that, because the two glassfilms flowing over the channel fuse together, neither of the outsidesurfaces of the resulting glass article comes in contact with any partof the apparatus. Thus, the surface properties of the fusion drawnglass-based substrate are not affected by such contact. Where theglass-based substrates is a glass ceramic, the glass-based substratesformed from the fusion process may be subjected to a ceramming processby which one or more crystalline phases are generated.

The slot draw process is distinct from the fusion draw method. In slotdraw processes, the molten raw material glass is provided to a drawingtank. The bottom of the drawing tank has an open slot with a nozzle thatextends the length of the slot. The molten glass flows through theslot/nozzle and is drawn downward as a continuous glass-based substrateand into an annealing region. Where the glass-based substrate is a glassceramic, the glass-based substrate formed from the slot draw process maybe subjected to a ceramming process by which one or more crystallinephases are generated.

In some embodiments, the glass-based substrate may be formed using athin rolling process, as described in U.S. Pat. Nos. 8,713,972,9,003,835, U.S. Patent Publication No. 2015/0027169, and U.S. PatentPublication No. 20050099618, the contents of which are incorporatedherein by reference in their entirety. More specifically the glass orglass-ceramic article may be formed by supplying a vertical stream ofmolten glass, forming the supplied stream of molten glass orglass-ceramic with a pair of forming rolls, maintained at a surfacetemperature of about 500° C. or higher or about 600° C. or higher, toform a formed glass ribbon having a formed thickness, sizing the formedribbon of glass with a pair of sizing rolls, maintained at a surfacetemperature of about 400° C. or lower to produce a sized glass ribbonhaving a desired thickness less than the formed thickness and a desiredthickness consistency. The apparatus used to form the glass ribbon mayinclude a glass feed device for supplying a supplied stream of moltenglass; a pair of forming rolls maintained at a surface temperature ofabout 500° C. or higher, the forming rolls being spaced closely adjacenteach other, defining a glass forming gap between the forming rolls withthe glass forming gap located vertically below the glass feed device forreceiving the supplied stream of molten glass and thinning the suppliedstream of molten glass between the forming rolls to form a formed glassribbon having a formed thickness; and a pair of sizing rolls maintainedat a surface temperature of about 400° C. or lower, the sizing rollsbeing spaced closely adjacent each other, defining a glass sizing gapbetween the sizing rolls with the glass sizing gap located verticallybelow the forming rolls for receiving the formed glass ribbon andthinning the formed glass ribbon to produce a sized glass ribbon havinga desired thickness and a desired thickness consistency.

In some instances, the thin rolling process may be utilized where theviscosity of the glass does not permit use of fusion or slot drawmethods. For example, thin rolling can be utilized to form the glass orglass-ceramic articles when the glass exhibits a liquidus viscosity lessthan 100 kP. The glass or glass-ceramic article may be acid polished orotherwise treated to remove or reduce the effect of surface flaws.

In contemplated embodiments, the glass-based substrates or articlesdiscussed herein has a composition that differs by side surface. On oneside of the glass or glass-ceramic sheet 500, an exemplary compositionis: 69-75 wt. % SiO₂, 0-1.5 wt. % Al₂O₃, 8-12 wt. % CaO, 0-0.1 wt. % Cl,0-500 ppm Fe, 0-500 ppm K, 0.0-4.5 wt. % MgO, 12-15 wt. % Na₂O, 0-0.5wt. % SO₃, 0-0.5 wt. % SnO₂, 0-0.1 wt. % SrO, 0-0.1 wt. % TiO₂, 0-0.1wt. % ZnO, and/or 0-0.1 wt. % ZrO₂. On the other side of the glass-basedsubstrates or articles discussed herein an exemplary composition is:73.16 wt. % SiO₂, 0.076 wt. % Al₂O₃, 9.91 wt. % CaO, 0.014 wt. % Cl, 0.1wt. % Fe₂O₃, 0.029 wt. % K₂O, 2.792 wt. % MgO, 13.054 wt. % Na₂O, 0.174wt. % SO₃, 0.001 SnO₂, 0.01 wt. % SrO, 0.01 wt. % TiO₂, 0.002 wt. % ZnO,and/or 0.005 wt. % ZrO₂.

In other contemplated embodiments, composition of the glass-basedsubstrates or articles discussed herein includes SiO₂ 55-85 wt. %, Al₂O₃0-30 wt. %, B₂O₃ 0-20 wt. %, Na₂O 0-25 wt. %, CaO 0-20 wt. %, K₂O 0-20wt. %, MgO 0-15 wt. %, BaO 5-20 wt. %, Fe₂O₃ 0.002-0.06 wt. %, and/orCr₂O₃ 0.0001-0.06 wt. %. In other contemplated embodiments, compositionof the glass-based substrates or articles discussed herein includes SiO₂60-72 mol. %, Al₂O₃ 3.4-8 mol. %, Na₂O 13-16 mol. %, K₂O 0-1 mol. %, MgO3.3-6 mol. %, TiO₂ 0-0.2 mol. %, Fe₂O₃ 0.01-0.15 mol. %, CaO 6.5-9 mol.%, and/or SO₃ 0.02-0.4 mol. %.

Another aspect of this disclosure pertains to a method for strengtheninga glass substrate. In one or more embodiments, the method includescooling a glass substrate (which may be in sheet form) having atransition temperature from a temperature greater than the transitiontemperature to a temperature less than the transition temperature bytransferring thermal energy from the glass sheet to a heat sink byconduction across a gap that is free of solid or liquid matter toprovide a thermally strengthened glass article, and then chemicallystrengthening the thermally strengthened glass article. In one or moreembodiments, the method includes transferring thermal energy from theglass sheet to a heat sink by conduction such that more than 20% of thethermal energy leaving the glass sheet crosses the gap and is receivedby the heat sink to thermally strengthen the glass sheet. In someinstances, about 25% or more, about 30% or more, about 35% or more,about 40% or more, about 45% or more, about 50% or more, or about 60% ormore of the thermal energy is transferred by conduction from the glasssheet to a heat sink across the gap. In some embodiments, the coolingrate may be about −270° C./second or greater (e.g., −280° C./second orgreater, −290° C./second or greater, −300° C./second or greater, −310°C./second or greater, or −320° C./second or greater).

In one or more embodiments, the thermally strengthened glass article ischemically strengthened without removing any portion of the thermallystrengthened glass sheet. For example, the thermally strengthened glassarticle is chemically strengthened without removing 3% or more (or 2% ormore, or 1% or more) of the thickness of the thermally strengthenedglass article.

In some embodiments, the thermally strengthened glass article comprisesa thickness and a DOC greater than or equal to 0.17 times the thicknessof the thermally strengthened glass article. In some instances, thethermally and chemically strengthened glass article exhibits a thicknessand a DOC greater than or equal to 0.17 times the thickness. In one moreembodiments, chemically strengthening the thermally strengthened glassarticles comprises generating a surface CS of about 700 MPa or greater,while maintaining the DOC.

In accordance with one or more embodiments, chemically strengthening thethermally strengthened article sheet comprises generating a chemicallystrengthened region that extends from a first surface of the glass-basedlayer to a DOL that is greater than or equal to about 10 micrometers.

The method of one or more embodiments, chemically strengthening thethermally strengthened glass article comprises immersing the thermallystrengthened glass sheet in a molten salt bath comprising any one ormore of KNO₃, NaNO₃, and LiNO₃. In some embodiments, the molten saltbath comprises KNO₃ and NaNO₃ and has a temperature in the range fromabout 380° C. to about 430° C.

Another aspect of this disclosure pertains to a consumer electronicproduct that includes a housing having a front surface, a back surfaceand side surfaces, electrical components including at least acontroller, a memory, a display and a cover article. In one or moreembodiments, the electrical components may be housed in or provided atleast partially inside to the housing. The display of one or moreembodiments may be provided at or adjacent the front surface of thehousing. In some embodiments, the cover article is provided at or overthe front surface of the housing over the display. The cover glass-basedarticle may include one or more embodiments of the thermally andchemically strengthened glass-based articles described herein. Theconsumer electronic device of one or more embodiments may be a mobilephone, portable media player, wearable electronic device (e.g. watch,fitness monitor) notebook computer or tablet computer.

Referring now to FIG. 14A, the glass-based article of one or moreembodiments 1310 may have curvature and/or a variable cross-sectionaldimension D. Such articles may have thicknesses disclosed herein as anaverage of dimension D or as a maximum value of dimension D. While theglass-based article 1310 is shown as a curved sheet, other shapes, suchas more complex shapes, may be strengthened by processes disclosedherein. In contemplated embodiments, the glass-based article 1310 may beused as a window for an automobile (e.g., sunroof), as a lens, as acontainer, or for other applications.

In some embodiments, the glass-based articles described herein have oneor more coatings that are placed on the glass prior to the thermalstrengthening of the glass sheet. The processes discussed herein can beused to produce strengthened glass sheets having one or more coatings,and, in some such embodiments, the coating is placed on the glass priorto thermal strengthening and is unaffected by the thermal strengtheningprocess. Specific coatings that are advantageously preserved on glasssheets of the present disclosure include low E coatings, reflectivecoatings, antireflective coatings, anti-fingerprint coatings, cut-offfilters, pyrolytic coatings, etc.

Another aspect of this disclosure pertains to laminates that include theglass-based articles described herein. For example, in one or moreembodiments, the laminate may include a first glass-based sheet 16, asecond glass-based sheet 12 and an interlayer 14 disposed between thefirst glass-based sheet and the second glass-based sheet, where one orboth the first glass-based sheet and the second glass-based sheet isthermally and chemically strengthened as described herein, as shown inFIG. 14B.

In one or more embodiments, the one of the first glass-based sheet andthe second glass-based sheet may be cold-formed. In an exemplary coldforming method shown in FIG. 14C, a glass sheet 16 can be laminated to arelatively thicker and curved glass sheet 12. The result of this coldformed lamination is that the surface of the thin glass sheet 17adjacent the interlayer 14 will have a reduced level of compression thanthe opposing surface 19 of the thin glass sheet. Furthermore, this coldform lamination process can result in a high compressive stress level onsurface 19 making this surface more resistant to fracture from abrasionand can add further compressive stress on the surface 13 of the thicker,glass sheet 12 also making this surface more resistant to fracture fromabrasion. In some non-limiting embodiments, an exemplary cold formingprocess can occur at or just above the softening temperature of theinterlayer material (e.g., about 100° C. to about 120° C.), that is, ata temperature less than the softening temperature of the respectiveglass sheets. Such a process can occur using a vacuum bag or ring in anautoclave or another suitable apparatus. FIGS. 14D-14E are crosssectional stress profiles of an exemplary inner glass layer according tosome embodiments of the present disclosure. It can be observed in FIG.14D that the stress profile for the thin glass sheet 16 exhibitssubstantially symmetrical compressive stresses on the surfaces 17, 19thereof with a central tension region. With reference to FIG. 14E, itcan be observed that the stress profile for the thin glass sheet 16,according to an exemplary cold formed embodiment, provides a shift incompressive stress, namely, the surface 17 adjacent the interlayer 14has a reduced compressive stress in comparison to the opposing surface19. This difference in stress can be explained using the followingrelationship:

σ=Ey/p

where E represents the modulus of elasticity of the beam material, yrepresents the perpendicular distance from the centroidal axis to thepoint of interest (surface of the glass), and p represents the radius ofcurvature to the centroid of the glass sheet. It follows that thebending of the glass sheet 16 via cold forming can induce a mechanicaltensile stress or a reduced compressive stress on the surface 17adjacent the interlayer 14 in comparison to the opposing surface 19 ofthe glass sheet 16.

In one or more embodiments, the laminates may include an interlayercomprising a polymeric material such as, but not limited to, poly vinylbutyral (PVB), polycarbonate, acoustic PVB, ethylene vinyl acetate(EVA), thermoplastic polyurethane (TPU), ionomer, a thermoplasticmaterial, and combinations thereof.

In some embodiments, the first glass-based sheet is complexly-curved andhas at least one concave surface providing a first surface of thelaminate and at least one convex surface to provide a second surface ofthe laminate opposite the first surface with a thickness therebetween,and the second glass-based sheet is complexly-curved and has at leastone concave surface to provide a third surface of the laminate and atleast one convex surface to provide a fourth surface of the laminateopposite the third surface with a thickness therebetween. In suchembodiments, the third and fourth surfaces respectively have CS valuessuch that the fourth surface has a CS value that is greater than the CSvalue of the third surface.

As used herein “complex curve”, “complexly curved”, “complex curvedsubstrate” and “complexly curved substrate” mean a non-planar shapehaving simple or compound curves, also referred to as non-developableshapes, which include but are not limited to a spherical surface, anaspherical surface, and a toroidal surface, where the curvature of twoorthogonal axes (horizontal and vertical one) are different, which maybe for example a toroidal shape, spheroid, and ellipsoid. The complexlycurved laminates according to embodiments may also include segments orportions of such surfaces, or be comprised of a combination of suchcurves and surfaces. In one or more embodiments, a laminate may have acompound curve including a major radius and a cross curvature. Acomplexly curved laminate according to embodiments may have a distinctradius of curvature in two independent directions. According to one ormore embodiments, complexly curved laminates may thus be characterizedas having “cross curvature,” where the laminate is curved along an axisthat is parallel to a given dimension and also curved along an axis thatis perpendicular to the same dimension. The curvature of the laminatecan be even more complex when a significant minimum radius is combinedwith a significant cross curvature, and/or depth of bend. Some laminatesmay also include bending along axes of bending that are notperpendicular to the longitudinal axis of the flat glass substrate. As anon-limiting example, an automobile sunroof typically measures about 0.5m by 1.0 m and has a radius of curvature of 2 to 2.5 m along the minoraxis, and a radius of curvature of 4 to 5 m along the major axis.

In one or more embodiments, the interlayer may include polyvinyl butyral(PVB) resin, ethylenevinylacetate copolymer or polyurethanesthermoplastic (TPU).

In one or more embodiments, one of the first glass-based substrate orthe second glass-based substrate has a thickness in the range of about0.2 mm to about 0.7 mm. In some embodiments, the fourth surface of thelaminate has a greater CS than the fourth surface has in a flat stateand the laminate is free from optical distortions. In one or morevariations, a peripheral portion of the second glass-based substrateexerts a compressive force against the interlayer, and a center portionof the second glass-based substrate exerts a tensile force against theinterlayer. In some instances, the second glass-based substrate conformsto the first glass-based substrate to provide a substantially uniformdistance between the convex surface of the second glass-based substrateand the concave surface of the first glass-based substrate, which isfilled by the intervening interlayer.

Another aspect of this disclosure pertains to a vehicle comprising anopening; and a laminate as described herein disposed in the opening. Thethickness of the laminate may vary according to the vehicle. Forexample, the vehicle may include a heavy truck and the laminate may havea thickness greater than about 3 mm. In some embodiments, the vehiclemay include a passenger car or truck and may have a thickness of about2.6 mm or less.

EXAMPLES

Various embodiments will be further clarified by the following examples.In the following examples, the glass-based substrate at a specifiedthickness, t, was thermally strengthened from a desired initialtemperature, T_(o), at the desired heat-transfer coefficient, h.

The thermal strengthening apparatus included three zones—a hot zone, atransition zone, and a cool or quench zone. The apparatus included topand bottom thermal bearings (or heat sinks) and the gaps between the topand bottom thermal bearings in the hot zone and the quench zone are setto the desired spacing. Gas flow rates in the hot zone, transition zone,and quench zone are set to ensure centering of the glass-based substrateon the air-bearing. The hot zone is pre-heated to the desired T₀, thetemperature from which the glass-based substrate will be subsequentlyquenched at high heat transfer rates (h, in units of cal/cm²-s-° C.). Toensure uniform heating, glass-based substrates are pre-heated in aseparate pre-heating apparatus, such as a batch or continuous furnace.Generally, glass-based substrates are pre-heated for greater than 5minutes prior to loading in the hot zone. For soda-lime glass-basedsubstrates, pre-heating is done around 450° C. After the pre-heat phase,the glass-based substrate is loaded into the hot zone and allowed toequilibrate, where equilibration is where the glass is uniformly at T₀.T₀ can be determined by the level of thermal strengthening desired, butis generally kept in the range between the softening point and the glasstransition temperature. The time to equilibration is dependent at leaston the thickness of the glass-based substrate. For example, forglass-based substrates in sheet form having a thickness of approximately1.1 mm or less, equilibration occurs in approximately 10 seconds. For 3mm-thick glass-based substrates in sheet form, equilibration occurs inapproximately 10 seconds to 30 seconds. For thicker sheets, up toapproximately 6 mm, the equilibration time may be on the order of 60seconds. Once the glass-based substrate has equilibrated to T₀, it israpidly transferred through the transition zone on air bearings and intothe cool or quench zone. The glass-based substrate rapidly quenches inthe quench zone to a temperature below the glass transition temperature,Tg. The glass-based substrate can be maintained in the quench zone forany period of time from 1 second, 10 seconds, or to several minutes ormore, depending on the degree of quench desired and/or the desiredtemperature of the resulting glass-based article at removal. Uponremoval the glass-based article is optionally allowed to cool beforehandling.

As the examples demonstrate, there is no limit on thickness except forthe limitations imposed by the thermal strengthening process (i.e., thechosen heat-transfer coefficient, h). That is, in traditional thermalstrengthening processes, the thickness is limited to greater than about1.5 mm, whereas the following examples demonstrate that embodiments ofthe present disclosure may be significantly thinner. In the followingexamples, the initial temperature T₀ was typically chosen to besomewhere between the softening point of the glass-based substrate andabout 100° C. lower than that softening point.

After being thermally strengthened, the glass-based articles were thensubjected to a chemical strengthening process by immersing in a moltensalt bath. The molten bath composition and duration of immersion aredescribed below. As is demonstrated herein, in some embodiments, thetemperature at which the chemical strengthening process is performed islow enough as to not anneal out or reduce the CS generated by thethermal strengthening process, but high enough to obtain the desired DOLand the desired DOL in a short amount of time. As the thermallystrengthened glass-based article has a very high fictive temperature,the viscosity of the glass-based article is non-equilibrium and stressrelaxation at elevated temperatures will occur much faster thanpredicted from the equilibrium viscosity curve.

The resulting thermally strengthened and chemically strengthenedglass-based article can be characterized by two simple techniques: 1)the surface CS, CS, and DOL can be measured using the FSM technique; and2) CT and DOC were measured using SCALP.

In some embodiments, the effects of the thermal strengthening andchemical strengthening processes on the mechanical performance of theglass-based articles described herein can be evaluated by various waysincluding but not limited to: drop testing, scratch testing, indentationtesting, and 4-point bending. Without being bound by theory, theperformance of the glass-based articles described herein can bepredicted by the CS, CT, DOC, and/or DOL values exhibited. For example,higher surface CS provides significant improvement in bending,scratching, and indentation testing. The high fictive temperatureprovides improved damage resistance in indentation and scratch testing.Drop testing is a damage-tolerance test and is more strongly affectedthe DOC, and perhaps even the fictive temperature. Therefore, theglass-based articles of one or more embodiments, which are subjected tothermal strengthening and chemical strengthening described herein,outperform glass-based articles that are strengthened by thermalstrengthening or chemical strengthening processes alone or using acombination of known thermal strengthening and chemical strengtheningprocesses. This improved performance is exhibited by a variety ofdifferent glass-based compositions.

Example 1

Glass-based substrates having a nominal composition of 69 mol % SiO₂,8.5 mol % Al₂O₃, 14 mol % Na₂O, 1.2 mol % K₂O, 6.5 mol % MgO, 0.5 mol %CaO, and 0.2 mol % SnO₂ and having identical thicknesses were fictivatedat various temperatures in the range from about 575° C. to about 725° C.to demonstrate the improved chemical strengthening achievable after theglass-based substrates are thermally strengthened (or strengthened toincrease the fictive temperature of such substrates). In other words,the glass-based substrates were heated to a T₀ in the range from about575° C. to about 725° C. for approximately three times the structuralrelaxation time and then quenched to room temperature to freeze in thehigh temperature state.

Glass-based substrates having the same nominal composition and thicknesswere also thermally strengthened by heating to a T₀ of 800° C. and thenquenching at heat transfer rates (h) of 0.069 cal/cm²-s-° C., 0.028cal/cm²-s-° C., and 0.013 cal/cm²-s-° C., as shown in Table 4.

The resulting thermally strengthened glass-based articles were thenchemically strengthened by ion-exchange by immersing in a molten saltbath of 100% KNO₃ having a temperature of about 410° C. for variousdurations up to about 8 hours. The DOL of each of the thermally andchemically strengthened glass-based articles were evaluated by FSMtechnique, and ion exchange diffusion coefficients were estimated usingthe equation: DOL=2*1.4*SQRT(D*t) or 2*1.4*√(D*t), where D is thediffusion coefficient, as shown in Table 4.

As demonstrated in Table 4, the ion exchange diffusion coefficient ofthe thermally strengthened and chemically strengthened glass-basedarticles is observed to correspond to a high fictive temperature state.Specifically, more strongly or highly thermally strengthened glass-basedarticles exhibit a high fictive temperature and a higher diffusioncoefficient. The resulting thermally strengthened glass-based-articleexhibits a deep DOC and thus, subsequent chemically strengthening doesnot cause a significant decrease in the DOC (initially generated fromthe thermal strengthening process).

TABLE 4 Effects of fictive temperature and thermal tempering on the ionexchange diffusion coefficient of the glass-based articles of Example 1.Diffusion Fictive Temperature (° C.) Coefficient at 410° C. (cm²/sec)575 7.30 × 10⁻¹¹ 600 7.60 × 10⁻¹¹ 625 9.30 × 10⁻¹¹ 650 1.03 × 10⁻¹⁰ 6751.05 × 10⁻¹⁰ 685 1.06 × 10⁻¹⁰ 700 1.09 × 10⁻¹⁰ 725 1.18 × 10⁻¹⁰ Tempered(h = 0.013 cal/cm²-s-° C.) 8.39 × 10⁻¹¹ Tempered (h = 0.028 cal/cm²-s-°C.) 8.76 × 10⁻¹¹ Tempered (h = 0.069 cal/cm²-s-° C.) 1.21 × 10⁻¹⁰

Example 2

Glass substrates having the same composition as the glass substrates ofExample 1 and having a thickness of about 1.1 mm were thermallystrengthened at various heat transfer rates and then chemicallystrengthened, as shown in Table 5.

Specifically, Example 2A-1 included a thermally strengthened glass-basedarticle that was heated to a T₀ of about 800° C. and then quenched ath=0.069 cal/cm²-s-° C., Example 2B-1 included a thermally strengthenedglass-based article that was heated to a T₀ of about 800° C. and thenquenched at h=0.028 cal/cm²-s-° C., and Example 2C-1 included athermally strengthened glass-based article that was heated to a T₀ ofabout 800° C. and then quenched at h=0.013 cal/cm²-s-° C. Examples 2A-2through 2A-5, 2B-2 through 2B-5, and 2C-2 through 2C-5 included glassarticles that included the same glass substrate and were thermallystrengthened in the same manner as Examples 2A-1, 2B-1 and 2C-1,respectively, but then were chemically strengthened by ion-exchange byimmersing in a molten salt bath of 100% KNO₃ having a temperature of410° C. for various times between 10 minutes and 1 hour, according toTable 5.

TABLE 5 Thermal strengthening and chemical strengthening conditions forExamples 2A-1 through 2A-5, 2B-1 through 2B-5, and 2C-1 through 2C-5.Chemical Thermal strengthening strengthening conditions (T₀, h) durationEx. 2A-1 T₀ = 800° C. None h = 0.069 cal/cm²-s-° C. Ex. 2A-2 T₀ = 800°C. 10 minutes h = 0.069 cal/cm²-s-° C. Ex. 2A-3 T₀ = 800° C. 15 minutesh = 0.069 cal/cm²-s-° C. Ex. 2A-4 T₀ = 800° C. 30 minutes h = 0.069cal/cm²-s-° C. Ex. 2A-5 T₀ = 800° C. 60 minutes h = 0.069 cal/cm²-s-° C.Ex. 2B-1 T₀ = 800° C. None h = 0.028 cal/cm²-s-° C. Ex. 2B-2 T₀ = 800°C. 10 minutes h = 0.028 cal/cm²-s-° C. Ex. 2B-3 T₀ = 800° C. 15 minutesh = 0.028 cal/cm²-s-° C. Ex. 2B-4 T₀ = 800° C. 30 minutes h = 0.028cal/cm²-s-° C. Ex. 2B-5 T₀ = 800° C. 60 minutes h = 0.028 cal/cm²-s-° C.Ex. 2C-1 T₀ = 800° C. None h = 0.013 cal/cm²-s-° C. Ex. 2C-2 T₀ = 800°C. 10 minutes h = 0.013 cal/cm²-s-° C. Ex. 2C-3 T₀ = 800° C. 15 minutesh = 0.013 cal/cm²-s-° C. Ex. 2C-4 T₀ = 800° C. 30 minutes h = 0.013cal/cm²-s-° C. Ex. 2C-5 T₀ = 800° C. 60 minutes h = 0.013 cal/cm²-s-° C.

Comparative Example 2D included the same glass substrate as Examples2A-1 through 2A-5, 2B-1 through 2B-5, and 2C-1 through 2C-5, but wassubjected only to a known chemical strengthening process (and notthermally strengthened) including immersion in a 100% KNO₃ molten saltbath having a temperature of 420° C. for 5.5 hours. The CS, CT, DOL andDOC values (as an absolute measurement and as a percentage of the glassarticle thickness) of all the resulting glass articles were measured andare shown in Tables 6-8. As shown in Tables 6-8, Comparative Example 2Dexhibited a DOL of about 44 micrometers and a surface CS of about 750MPa. By selecting the instant chemical strengthening conditions, thethermally strengthened and chemically strengthened glass articles ofExamples 2A-2C exhibit comparable surface CS values as ComparativeExample 2D, but from a significantly shorter immersion (or chemicalstrengthening duration), while also exhibiting a total DOC that is manytimes larger than achievable by a chemical strengthening process alone.

TABLE 6 Measured properties of the resulting thermally and chemicallystrengthened glass articles of Example 2A-1 through 2A-5, andComparative Example 2D. DOL DOC CS CT (in DOC (in as % of articleExample (MPa) (MPa) μm) μm) thickness Ex. 2A-1 165 71 0 250 22.9 Ex.2A-2 766 57 9.0 240 22.0 Ex. 2A-3 753 57 11.3 236 21.6 Ex. 2A-4 760 5814.1 236 21.6 Ex. 2A-5 746 62 20.2 215 19.7 Comparative Ex. 752 31 44.344 4.1 2D

TABLE 7 Measured properties of the resulting thermally and chemicallystrengthened glass articles of Example 2B-1 through 2B-5, andComparative Example 2D. DOL DOC CS CT (in DOC (in as % of articleExample (MPa) (MPa) μm) μm) thickness Ex. 2B-1 73 48 0 210 19.3 Ex. 2B-2846 32 8.6 205 18.8 Ex. 2B-3 837 33 10.0 194 17.8 Ex. 2B-4 826 34 13.6182 16.7 Ex. 2B-5 817 36 17.9 167 15.3 Comparative Ex. 752 31 44.3 444.1 2D

TABLE 8 Measured properties of the resulting thermally and chemicallystrengthened glass articles of Example 2C-1 through 2C-5, andComparative Example 2D. DOL DOC CS CT (in DOC (in as % of articleExample (MPa) (MPa) μm) μm) thickness Ex. 2C-1 47 33 0 200 18.3 Ex. 2C-2833 35 8.0 181 16.6 Ex. 2C-3 837 37 9.5 173 15.9 Ex. 2C-4 831 38 13.0162 14.8 Ex. 2C-5 813 40 17.1 142 13.0 Comparative Ex. 752 31 44.3 444.1 2D

By thermally strengthening at higher heat transfer rates (or generatinga more strongly thermally strengthened glass article), high surface CSvalues can be generated by subsequent chemical strengthening withoutsignificantly decreasing the DOC generated by the thermal strengtheningprocess. As shown in Tables 6-8, the glass articles that were thermallystrengthened at higher heat transfer rates (i.e., h=0.069 cal/cm²-s-°C.) maintained DOC values after being chemically strengthened. Themaintenance of DOC values is also shown in FIG. 15, which shows theglass articles of Example 2A, which were thermally strengthened at ahigh heat transfer rate exhibited significantly shallower slope ordecrease in DOC, with increasing DOL.

The glass substrates (prior to being thermally and/or chemicallystrengthened) of Example 2, the thermally strengthened glass articles ofExamples 2A-1, 2B-1 and 2C-1, the thermally and chemically strengthenedglass articles of Examples 2A-2, 2B-2 and 2C-2, and the chemicallystrengthened glass article of Comparative Example 2D were compared interms of mechanical performance. Specifically, samples of these glasssubstrates or articles were subjected to an incremental drop test (usingtwo different types of sandpaper drop surfaces), a four-point bend test,a Vicker's indentation threshold test and a Knoop scratch thresholdtest. The results of each test are shown in Table 9.

In incremental drop testing, the glass substrates or articles were sizedto have dimensions of approximately 50 mm×110 mm and then glued toidentical mobile phone housings. The assemblies were then eachsuccessively dropped onto 180 grit sandpaper in 20 cm height intervalsstarting at 20 cm up to 220 cm. The assemblies were dropped so the glasssubstrates or articles impacted the sandpaper. Glass which survived alldrops to a drop height of 220 cm are then dropped on 30 grit sandpaperfrom the same height intervals until failure occurs. The average dropheight is shown in Table 9. The incremental drop test provides a roughevaluation of the glass performance when repeatedly damaged.

In four-point bending, samples of each of the glass substrates orarticles were subjected to a bending load of 5 mm/minute, using an 18 mmload span and 36 mm support span, with tape on the side of compression,and Teflon surface in contact with the side of the sample in tension,and samples were tested until failure. Samples that failed under theloading knife were not considered.

In Vicker's indentation threshold testing, samples of the glasssubstrates and articles were repeatedly indented with a diamond tip (at136° angle) at increasing loads. Each indentation has the potential toproduce 4 radial cracks, one from each corner of the indent. By countingthe average number of radial cracks at each indentation load, thecracking threshold can be defined by the load at which there is anaverage of 2 cracks per indent (or the 50% cracking threshold).

In Knoop scratch threshold testing, samples of the glass substrates andarticles were first scratched with a Knoop indenter under a dynamic orramped load to identify the lateral crack onset load range for thesample population. Once the applicable load range is identified, aseries of increasing constant load scratches (3 minimum or more perload) are performed to identify the Knoop scratch threshold. The Knoopscratch threshold range can be determined by comparing the test specimento one of the following 3 failure modes: 1) sustained lateral surfacecracks that are more than two times the width of the groove, 2) damageis contained within the groove, but there are lateral surface cracksthat are less than two times the width of groove and there is damagevisible by naked eye, or 3) the presence of large subsurface lateralcracks which are greater than two times the width of groove and/or thereis a median crack at the vertex of the scratch.

TABLE 9 Mechanical performance of the unstrengthened glass substrate ofExample 2, and the glass articles of Examples 2A-1, 2A-2, 2B-1, 2B-2,2C-1 and 2C-2 and Comparative Example 2D. 180 grit 30 grit drop drop4-PB Vicker's Knoop (cm) (cm) (MPa) (N) (N) Unstrengthened glasssubstrate of — — 173 <2 6-8 Example 2 Comparative Example 2D 86 24 68340-50 4-6 (chemically strengthened only, at 420° C. for 5.5 hours)Example 2A-1 196 117 296 20-30 4-6 (thermally strengthened only at T₀ =800° C., h = 0.058) Example 2A-2 204 176 717 150-200 12-14 (thermallystrengthened at T₀ = 800° C., h = 0.058, and chemically strengthened at410° C. for 10 min) Example 2B-1 182 120 290 4-6 4-6 (thermallystrengthened only at T₀ = 800° C., h = 0.028) Example 2B-2 220 152 661150-200 10-12 (thermally strengthened at T₀ = 800° C., h = 0.028, andchemically strengthened at 410° C. for 10 min) Example 2C-1 <2 4-6(thermally strengthened only at T₀ = 800° C., h = 0.013) Example 2C-2100-150  8-10 (thermally strengthened at T₀ = 800° C., h = 0.013, andchemically strengthened at 410° C. for 10 min)

Example 3

Glass substrates having the same composition as the glass substrates ofExample 1 and having a thickness of about 0.7 mm were thermallystrengthened at various heat transfer rates and then chemicallystrengthened, as shown in Table 10.

Specifically, Example 3A-1 included a thermally glass article that washeated to a T₀ of about 800° C. and then quenched at h=0.073 cal/cm²-s-°C. Examples 3A-2 through 3A-4 included glass articles that included thesame glass substrate and were thermally strengthened in the same manneras Example 3A-1, but were then chemically strengthened by ion-exchangeby immersing in a molten salt bath of 100% KNO₃ having a temperature of410° C. for various times between 10 minutes and 1 hour, according toTable 10.

TABLE 10 Thermal strengthening and chemical strengthening conditions forExamples 3A-1 through 3A-4. Chemical Thermal strengthening strengtheningconditions (T₀, h) duration Ex. 3A-1 T₀ = 800° C. None h = 0.073cal/cm²-s-° C. Ex. 3A-2 T₀ = 800° C. 10 minutes h = 0.073 cal/cm²-s-° C.Ex. 3A-3 T₀ = 800° C. 15 minutes h = 0.073 cal/cm²-s-° C. Ex. 3A-4 T₀ =800° C. 30 minutes h = 0.073 cal/cm²-s-° C.

Comparative Example 3B included the same glass substrate but wassubjected only to a known chemical strengthening process (and notthermally strengthened) including immersion in a 100% KNO₃ molten saltbath having a temperature of 420° C. for 5.5 hours. The CS, CT, DOL andDOC values (as an absolute measurement and as a percentage of the glassarticle thickness) of all the resulting glass articles were measured andare shown in Table 11. As shown in Table 11, Comparative Example 3Bexhibited a DOL of about 45 micrometers and a surface CS of about 710MPa. By selecting the instant chemical strengthening conditions, thethermally strengthened and chemically strengthened glass articles ofExamples 3A-1 through 3A-4 exhibit comparable surface CS values asComparative Example 3B, but from a significantly shorter immersion (orchemical strengthening duration), while also exhibiting a total DOC thatis many times larger than achievable by a chemical strengthening processalone.

TABLE 11 Measured properties of the resulting thermally and chemicallystrengthened glass articles of Example 3A-1 through 3A-4, andComparative Example 3B. DOL DOC CS CT (in DOC (in as % of articleExample (MPa) (MPa) μm) μm) thickness Ex. 3A-1 122 63 0 172 24.9 Ex.3A-2 737 49 7.6 155 22.4 Ex. 3A-3 742 48 10.5 135 19.5 Ex. 3A-4 728 5214.1 142 20.5 Comparative Ex. 710 43 44.8 44.8 6.5 3B

The glass substrates (prior to being thermally and/or chemicallystrengthened) of Example 3, the thermally strengthened glass articles ofExamples 3A-1 and 3A-2, and the chemically strengthened glass article ofComparative Example 3B were compared in terms of mechanical performance.Specifically, samples of these glass substrates or articles weresubjected to an incremental drop test (using two different types ofsandpaper drop surfaces) a four-point bend test, a Vicker's indentationthreshold test and a Knoop scratch threshold test, as described above inExample 2. The results of each test are shown in Table 12.

TABLE 12 Mechanical performance of the unstrengthened glass substrate ofExample 3, and the glass articles of Examples 3A-1 and 3A-2, andComparative Example 3B. 180 grit 4-PB Vicker's Knoop drop (cm) (MPa) (N)(N) Unstrengthened glass substrate of Example 3 — 121 4-6 2-4Comparative Example 3B 62 578 70-80 4-6 (chemically strengthened only,at 420° C. for 5.5 hours) Example 3A-1 116 267 20-30 4-6 (thermallystrengthened only at T₀ = 800° C., h = 0.073) Example 3A-2 104 628150-200 10-12 (thermally strengthened at T₀ = 800° C., h = 0.058, andchemically strengthened at 410° C. for 10 min)

Example 4

Glass substrates having the same composition as the glass substrates ofExample 1 and having a thickness of about 0.55 mm were thermallystrengthened at various heat transfer rates and then chemicallystrengthened, as shown in Table 13.

Specifically, Example 4A-1 included a thermally strengthened glassarticle that was heated to a T₀ of about 800° C. and then quenched ath=0.084 cal/cm²-s-° C. Examples 4A-2 through 4A-5 included glassarticles that included the same glass substrate and were thermallystrengthened in the same manner as Example 4A-1, but were thenchemically strengthened by ion-exchange by immersing in a molten saltbath of 100% KNO₃ having a temperature of 410° C. for various timesbetween 10 minutes and 1 hour, according to Table 13.

TABLE 13 Thermal strengthening and chemical strengthening conditions forExamples 4A-1 through 4A-5. Chemical Thermal strengthening strengtheningconditions (T₀, h) duration Ex. 4A-1 T₀ = 800° C. None h = 0.084cal/cm²-s-° C. Ex. 4A-2 T₀ = 800° C. 10 minutes h = 0.084 cal/cm²-s-° C.Ex. 4A-3 T₀ = 800° C. 15 minutes h = 0.084 cal/cm²-s-° C. Ex. 4A-4 T₀ =800° C. 30 minutes h = 0.084 cal/cm²-s-° C. Ex. 4A-5 T₀ = 800° C. 60minutes h = 0.084 cal/cm²-s-° C.

Comparative Example 4B included the same glass substrate but wassubjected only to a known chemical strengthening process (and notthermally strengthened) including immersion in a 100% KNO₃ molten saltbath having a temperature of 420° C. for 5.5 hours. The CS, CT, DOL andDOC values (as an absolute measurement and as a percentage of the glassarticle thickness) of all the resulting glass articles were measured andare shown in Table 14. As shown in Table 14, Comparative Example 4Bexhibited a DOL of about 44 micrometers and a surface CS of about 750MPa. By selecting the instant chemical strengthening conditions, thethermally strengthened and chemically strengthened glass articles ofExamples 4A-1 through 4A-5 exhibit comparable surface CS values asComparative Example 4B, but from a significantly shorter immersion (orchemical strengthening duration), while also exhibiting a total DOC thatis many times larger than achievable by a chemical strengthening processalone.

TABLE 14 Measured properties of the resulting thermally and chemicallystrengthened glass articles of Example 4A-1 through 4A-5, andComparative Example 4B. DOL DOC CS CT (in DOC (in as % of articleExample (MPa) (MPa) μm) μm) thickness Ex. 4A-1 116 53 0 131 23.7 Ex.4A-2 832 41 8.9 126 22.8 Ex. 4A-3 803 39 9.7 119 21.5 Ex. 4A-4 784 3813.3 112 20.3 Ex. 4A-5 770 38 19.3 106 19.2 Comparative Ex. 754 60 43.643.6 7.9 4B

The glass substrates (prior to being thermally and/or chemicallystrengthened) of Example 4, the thermally strengthened glass articles ofExamples 4A-1 and 4A-2, and the chemically strengthened glass article ofComparative Example 4B were compared in terms of mechanical performance.Specifically, samples of these glass substrates or articles weresubjected to a Vicker's indentation threshold test and a Knoop scratchthreshold test, as described above in Example 2. The results of eachtest are shown in Table 15.

TABLE 15 Mechanical performance of the unstrengthened glass substrate ofExample 4, and the glass articles of Examples 4A-1 and 4A-2, andComparative Example 4B. Vicker's Knoop (N) (N) Unstrengthened glasssubstrate of Example 4 <2  8-10 Comparative Example 4B 60-70 4-6(chemically strengthened only, at 420° C. for 5.5 hours) Example 4A-14-6 2-4 (thermally strengthened only at T₀ = 800° C., h = 0.073) Example4A-2 100-150 4-6 (thermally strengthened at T₀ = 800° C., h = 0.058, andchemically strengthened at 410° C. for 10 min)

Example 5

Glass substrates having a soda-lime silicate composition and having athickness of about 1.1 mm were thermally strengthened at various heattransfer rates and then chemically strengthened, as shown in Table 16.

Specifically, Example 5A-1 included a thermally strengthened glassarticle that was heated to a T₀ of about 710° C. and then quenched ath=0.086 cal/cm²-s-° C. Examples 5A-2 through 5A-9 were glass articlesthat included the same glass substrate and were thermally strengthenedin the same manner as Example 5A-1, but were then chemicallystrengthened by ion-exchange by immersing in a molten salt bath of 100%KNO₃ having a temperature in the range from about 380° C. to about 420°C. for various times between 30 minutes and 4 hours, according to Table16.

TABLE 16 Thermal strengthening and chemical strengthening conditions forExamples 5A-1 through 5A-9. Chemical strengthening Thermal strengtheningduration and conditions (T₀, h) temperature Ex. 5A-1 T₀ = 710° C. None h= 0.086 cal/cm²-s-° C. Ex. 5A-2 T₀ = 710° C. 4 hours h = 0.086cal/cm²-s-° C. 380° C. Ex. 5A-3 T₀ = 710° C. 4 hours h = 0.086cal/cm²-s-° C. 390° C. Ex. 5A-4 T₀ = 710° C. 2 hours h = 0.086cal/cm²-s-° C. 400° C. Ex. 5A-5 T₀ = 710° C. 4 hours h = 0.086cal/cm²-s-° C. 400° C. Ex. 5A-6 T₀ = 710° C. 2 hours h = 0.086cal/cm²-s-° C. 410° C. Ex. 5A-7 T₀ = 710° C. 4 hours h = 0.086cal/cm²-s-° C. 410° C. Ex. 5A-8 T₀ = 710° C. 2 hours h = 0.086cal/cm²-s-° C. 420° C. Ex. 5A-9 T₀ = 710° C. 4 hours h = 0.086cal/cm²-s-° C. 420° C.

The CS, CT, DOL and DOC values (as an absolute measurement and as apercentage of the glass article thickness) of all the resulting glassarticles were measured and are shown in Table 17. As shown in Table 17,by selecting the instant chemical strengthening conditions, thethermally strengthened and chemically strengthened glass articles ofExamples 5A-2 through 5A-9 exhibit high surface CS values from arelatively short immersion (or chemical strengthening duration), whilealso exhibiting a total DOC that is greater than 19% and even greaterthan 21% of the thickness (i.e., greater than 0.19●t or greater thanabout 0.21●t) of the glass article.

TABLE 17 Measured properties of the resulting thermally and chemicallystrengthened glass articles of Example 5A-1 through 5A-9. CT DOL DOC DOCas % of Example CS (MPa) (MPa) (in μm) (in μm) article thickness Ex.5A-1 188 89 0 234 21.7 Ex. 5A-2 700 48 5.5 227 21.0 Ex. 5A-3 643 39 6.1217 20.1 Ex. 5A-4 665 36 5.7 224 20.7 Ex. 5A-5 574 33 7.3 216 20.0 Ex.5A-6 623 32 6.0 226 20.9 Ex. 5A-7 556 28 8.5 212 19.6 Ex. 5A-8 603 256.4 217 20.1 Ex. 5A-9 538 24 9.2 213 19.7

The ion exchange diffusion coefficients (in units of cm²/second) wereestimated from the equation DOL=2*1.4*SQRT(D*t) or 2*1.4*√(D*t), where Dis the diffusion coefficient, using stress data obtained from FSM (andthe DOL information from Table 17). The ion-exchange diffusioncoefficient of the same the glass substrate before thermal strengtheningand in the as-float conditions (Tf of approximately 550° C.) was alsoestimated by the same method and equation. The results of the comparisonare shown in Table 18 and FIG. 16. As shown in Table 18 and FIG. 16, atany given temperature, the ion exchange diffusion coefficient of thesoda-lime glass substrate has been increased by a factor of 2 after theglass substrate has been thermally strengthened, as described herein.

TABLE 18 Ion exchange diffusion coefficient of the glass substrates andthermally strengthened glass articles of Example 5. Ion ExchangeAs-Floated After Thermally Strengthening (h = Temperature (° C.) (T_(f)≈550° C.) 0.086 and T_(f)≈ 660° C.) 380 1.38 × 10⁻¹² 2.65 × 10⁻¹² 3901.87 × 10⁻¹² 3.33 × 10⁻¹² 400 2.48 × 10⁻¹² 4.72 × 10⁻¹² 410 3.24 × 10⁻¹²6.38 × 10⁻¹² 420 4.46 × 10⁻¹² 7.55 × 10⁻¹²

Example 6

Glass substrates having a nominal composition of 57.5 mol % SiO₂, 16.5mol % Al₂O₃, 16 mol % Na₂O, 2.8 mol % MgO and 6.5 mol % P₂O₅, and havinga thickness of about 0.8 mm were thermally strengthened at various heattransfer rates and then chemically strengthened, as shown in Table 19.

Specifically, Example 6A-1 included a thermally strengthened glassarticle that was heated to a T₀ of about 830° C. and then quenched ath=0.025 cal/cm²-s-° C., Example 6B-1 included a thermally strengthenedglass article that was heated to a T₀ of about 830° C. and then quenchedat h=0.045 cal/cm²-s-° C., and Example 6C-1 included a thermallystrengthened glass article that was heated to a T₀ of about 830° C. andthen quenched at h=0.080 cal/cm²-s-° C. Examples 6A-2 through 6A-4, 6B-2through 6B-4, and 6C-2 through 6C-4 included glass articles thatincluded the same glass substrate and were thermally strengthened in thesame manner as Examples 6A-1, 6B-1 and 6C-1, respectively, but were thenchemically strengthened by ion-exchange by immersing in a molten saltbath of 100% KNO₃ having a temperature of about 390° C. for 15 minutes,30 minutes and 60 minutes, according to Table 19.

TABLE 19 Thermal strengthening and chemical strengthening conditions forExample 6. Chemical strengthening Thermal strengthening duration andconditions (T₀, h) temperature Ex. 6A-1 T₀ = 830° C. None h = 0.025cal/cm²-s-° C. Ex. 6A-2 T₀ = 830° C. 15 minutes h = 0.025 cal/cm²-s-° C.390° C. Ex. 6A-3 T₀ = 830° C. 30 minutes h = 0.025 cal/cm²-s-° C. 390°C. Ex. 6A-4 T₀ = 830° C. 60 minutes h = 0.025 cal/cm²-s-° C. 390° C. Ex.6B-1 T₀ = 830° C. None h = 0.045 cal/cm²-s-° C. Ex. 6B-2 T₀ = 830° C. 15minutes h = 0.045 cal/cm²-s-° C. 390° C. Ex. 6B-3 T₀ = 830° C. 30minutes h = 0.045 cal/cm²-s-° C. 390° C. Ex. 6B-4 T₀ = 830° C. 60minutes h = 0.080 cal/cm²-s-° C. 390° C. Ex. 6C-1 T₀ = 830° C. None h =0.080 cal/cm²-s-° C. Ex. 6C-2 T₀ = 830° C. 15 minutes h = 0.080cal/cm²-s-° C. 390° C. Ex. 6C-3 T₀ = 830° C. 30 minutes h = 0.080cal/cm²-s-° C. 390° C. Ex. 6C-4 T₀ = 830° C. 60 minutes h = 0.080cal/cm²-s-° C. 390° C.

The CS, CT, DOL and DOC values (as an absolute measurement and as apercentage of the glass article thickness) of all the resulting glassarticles were measured and are shown in Table 20. As demonstrated inTable 20 and FIG. 17, a greater the level of thermal strengtheningresults in a deeper DOC, which in turn is substantially maintained evenafter subsequent chemical strengthening. Accordingly, by thermallystrengthening to a greater degree, deeper DOL values and higher surfaceCS values can be achieved without sacrificing DOC.

TABLE 20 Measured properties of the resulting thermally and chemicallystrengthened glass articles of Example 6A-1 through 6A-4, 6B-1 through6B-4 and 6C-1 through 6C-4. DOL DOC DOC as % of Example CS (MPa) CT(MPa) (in μm) (in μm) article thickness Ex. 6A-1 72 36 — 172 21.5 Ex.6A-2 910 46 15.1 140 17.5 Ex. 6A-3 880 49 20.5 122 15.3 Ex. 6A-4 872 5226.9 113 14.1 Ex. 6B-1 100 49 — 185 23.1 Ex. 6B-2 929 55 15.1 148 18.5Ex. 6B-3 887 57 20.7 137 17.1 Ex. 6B-4 871 61 26.9 123 15.4 Ex. 6C-1 11559 — 196 24.5 Ex. 6C-2 891 65 15.2 170 21.3 Ex. 6C-3 878 67 20.6 15919.9 Ex. 6C-4 857 67 27.2 144 18.0

The ion exchange diffusion coefficients (in units of cm²/second) wereestimated from the equation DOL=2*1.4*SQRT(D*t) or 2*1.4*√(D*t), where Dis the diffusion coefficient, using stress data obtained from FSM (andthe DOL information from Table 19). The ion-exchange diffusioncoefficient of the same glass-based substrate was also measured afterthe glass substrate had been annealed at the glass transitiontemperature 1 hour (but not thermally strengthened or chemicallystrengthened). The results of the comparison are shown in Table 21 andin FIG. 17. As shown in Table 21 and FIG. 17, at any given temperaturethe ion exchange diffusion coefficient of the glass substrate has beenincreased by approximately a factor of 2 after the glass has undergonethermal strengthening as described herein.

TABLE 21 Ion exchange diffusion coefficient of the glass substrates andthermally strengthened glass articles of Example 6. IOX DiffusionCoefficient Condition at 390° C. (cm²/sec) Annealed 1.48 × 10⁻¹⁰ AfterThermally Strengthening h = 0.025 2.77 × 10⁻¹⁰ After ThermallyStrengthening h = 0.050  2.9 × 10⁻¹⁰ After Thermally Strengthening h =0.080 2.82 × 10⁻¹⁰

Example 7

Glass substrates having a nominal composition of 64 mol % SiO₂, 15.7 mol% Al₂O₃, 11 mol % Na₂O, 6.25 mol % Li₂O, 1.2 mol % ZnO, and 2.5 mol %P₂O₅, and having a thickness of about 0.8 mm were thermally strengthenedat various heat transfer rates and then chemically strengthened, asshown in Table 22.

Specifically, Example 7A-1 included a thermally strengthened glassarticle that was heated to a T₀ of about 810° C. and then quenched ath=0.078 cal/cm²-s-° C. Examples 7A-2 through 7A-5 were glass articlesthat included the same glass substrate and were thermally strengthenedin the same manner as Example 7A-1 but were then chemically strengthenedby ion-exchange by immersing in a molten salt bath of 100% KNO₃ having atemperature of about 380° C. and 390° C. for 15 minutes and 30 minutes,according to Table 22.

TABLE 22 Thermal strengthening and chemical strengthening conditions forExample 7. Chemical strengthening Thermal strengthening duration andconditions (T₀, h) temperature Ex. 7A-1 T₀ = 810° C. None h = 0.078cal/cm²-s-° C. Ex. 7A-2 T₀ = 810° C. 15 minutes h = 0.078 cal/cm²-s-° C.380° C. Ex. 7A-3 T₀ = 810° C. 30 minutes h = 0.078 cal/cm²-s-° C. 380°C. Ex. 7A-4 T₀ = 810° C. 15 minutes h = 0.078 cal/cm²-s-° C. 390° C. Ex.7A-5 T₀ = 810° C. 30 minutes h = 0.078 cal/cm²-s-° C. 390° C.

The CS, CT, DOL and DOC values (as an absolute measurement and as apercentage of the glass article thickness) of all the resulting glassarticles were measured and are shown in Table 23. As demonstrated inTable 23, by choosing the appropriate chemical strengthening conditions,a surface CS in excess of 1 GPa and DOC of more than 20% of thethickness can be achieved. In addition, the resulting thermally andchemically strengthened glass articles were not frangible when broken.

TABLE 23 Measured properties of the resulting thermally and chemicallystrengthened glass articles of Example 7A-1 through 7A-5. DOL DOC DOC as% of Example CS (MPa) CT (MPa) (in μm) (in μm) article thickness Ex.7A-1 128 64 0 198 24.4 Ex. 7A-2 1009 72 6.0 167 20.6 Ex. 7A-3 1018 707.3 163 20.1 Ex. 7A-4 1043 63 6.3 161 19.9 Ex. 7A-5 1055 77 7.9 150 18.6

The K₂O, Na₂O and Li₂O concentration as a function of depth of thethermally and chemically strengthened glass articles of Example 7A-3,7A-4 and 7A-5 were analyzed by microprobe. The results are shown inFIGS. 18, 19, and 20, respectively, which show a high concentration ofK₂O at the surface that decreases to about a depth of 6 micrometers(FIG. 18), 5.5 micrometers (FIG. 19) and 7.5 micrometers (FIG. 20). Theconcentration of Na₂O increases correspondingly to the decrease in K₂O.

Glass substrates having a nominal composition of 64 mol % SiO₂, 15.7 mol% Al₂O₃, 11 mol % Na₂O, 6.25 mol % Li₂O, 1.2 mol % ZnO, and 2.5 mol %P₂O₅, and having a thickness of about 0.8 mm were thermally strengthenedaccording the same conditions as Example 7A-1 to provide ComparativeExamples 7B-1 through 7B-4. Examples 7A-5 through 7A-8 were glassarticles that included the same glass substrates and were thermallystrengthened in the same manner as Comparative Examples 7B-1 through7B-4, but were then chemically strengthened in a mixed molten salt bathincluding 80% KNO₃ and 20% NaNO₃ and having a temperature of 390° C. for0.35 hours (to provide Ex. 7B-5), 1 hour (to provide Ex. 7B-6), 1.5hours (to provide Ex. 7B-7), and 2 hours (to provide Ex. 7B-8). Thestress profiles of Comparative Examples 7B-1 through 7B-4 and Examples7B-5 through 7B-8 were analyzed by SCALP and shown in FIGS. 21-24. Asshown in FIGS. 21-24, the surface CS value can be increased by more than100 MPa while still maintaining a deep DOC (or minimizing decreases inDOC), by chemically strengthening the thermally strengthened glassarticles. Without being bound by theory, the unique properties of thethermally strengthened glass articles permit chemical strengthening insuch a manner and the resulting properties in terms of stress profiles(CS, CT, DOL and DOC).

Glass substrates having the same composition and thickness as Examples7B-1 through 7B-8 were not thermally strengthened but were onlychemically strengthened by immersing in a molten salt bath of 80% KNO₃and 20% NaNO₃ and having a temperature of 390° C. for 0.35 hours(Comparative Example 7C-1), 1 hour (Comparative Example 7C-2), 1.5 hours(Comparative Example 7C-3) and 2 hours (Comparative Example 7C-4). Theresulting CT was plotted in FIG. 25, along with the CT of each of thethermally strengthened samples of Comparative Examples 7B-1 through7B-4, and each of thermally and chemically strengthened Examples 7B-5through 7B-8. FIG. 26 shows the change in CT (or delta CT) betweenComparative Example 7B-1 and Example 7B-5, between Comparative Example7B-2 and Example 7B-6, between Comparative Example 7B-3 and Example7B-7, between Comparative Example 7B-4 and Example 7B-8. FIG. 26demonstrates the change in CT before and after chemical strengthening,as a function of chemical strengthening time (or ion exchange time).

FIG. 27 plots the surface CS and the CS at the DOL, as a function ofchemical strengthening time (or ion exchange time) of each of Examples7B-5 through 7B-8. FIG. 28 shows the CS at the DOL, as a function of asa function of chemical strengthening time (or ion exchange time) of eachof Examples 7B-5 through 7B-8, along with the change in CT from FIG. 26.FIG. 29 shows the change in DOL of each of Examples 7B-5 through 7B-8.

Examples 7B-5 through 7B-8 were then fractured by impacting them with atungsten carbide scribe by hand. Examples 7B-6 through 7B-8 fracturedinto more and smaller pieces having a smaller aspect ratios than Example7B-5, which had significantly less CT compared to Examples 7B-6 through7B-8.

Glass substrates having the same composition and thickness as Examples7B-1 through 7B-8 were not thermally strengthened but were onlychemically strengthened by immersing in a molten salt bath of 80% KNO₃and 20% NaNO₃ and having a temperature of 390° C. for 4 hours(Comparative Example 7C-5), 8 hours (Comparative Example 7C-6), and 16hours (Comparative Example 7C-7). The surface CS of Comparative Examples7C-2 through 7C-7 and Examples 7B-5 through 7B-8 are plotted in FIG. 30,as a function of chemical strengthening time. The DOL of ComparativeExamples 7C-2 through 7C-7 and Examples 7B-5 through 7B-8 are plotted inFIG. 31, as a function of chemical strengthening time. The CS at DOL (orknee stress) of Comparative Examples 7C-2 through 7C-7 and Examples 7B-5through 7B-8 are plotted in FIG. 32, as a function of chemicalstrengthening time.

Example 8

Glass substrates having the same composition and thickness as thesubstrates used in Example 7 were thermally strengthened by heating tothe same T₀ value (i.e., 810° C.) and then quenching at different hvalues (i.e., h=0.025 cal/cm²-s-° C., h=0.050 cal/cm²-s-° C. and h=0.080cal/cm²-s-° C.), providing a high level, thermally strengthened glassarticle (Comparative Example 8A-1), medium level, thermally strengthenedglass article (Comparative Example 8B-1) and a low level thermallystrengthened glass article (Comparative Example 8C-1). The surface CS,knee CS, CT and DOC of three samples each of Comparative Examples 8A-1,8B-1 and 8C-1 were evaluated. Examples 8A-2 through 8A-4, Examples 8B-2through 8B-4 and Examples 8C-2 through 8C-4 included the same glasssubstrate as Example 7 and were thermally strengthened in the samemanner as Comparative Examples 8A-1, 8B-1 and 8C-1, respectively, butwere then chemically strengthened by immersing in a mixed molten saltbath (including NaNO₃ and KNO₃ having varying concentrations) having atemperature of 390° C. for 2 hours, as shown in Table 24.

TABLE 24 Thermal strengthening and chemical strengthening conditions forExample 8. Thermal strengthening Molten salt bath conditions (T₀, h)composition High level, Comparative Ex. 8A-1 T₀ = 810° C. Not chemicallythermally h = 0.080 cal/cm²-s-° C. strengthened strengthened Ex. 8A-2 T₀= 810° C.  80% KNO3 h = 0.080 cal/cm²-s-° C.  20% NaNO3 Ex. 8A-3 T₀ =810° C.  50% KNO3 h = 0.080 cal/cm²-s-° C.  50% NaNO3 Ex. 8A-4 T₀ = 810°C.  0% KNO3 h = 0.080 cal/cm²-s-° C. 100% NaNO3 Medium level,Comparative Ex. 8B-1 T₀ = 810° C. Not chemically thermally h = 0.050cal/cm²-s-° C. strengthened strengthened Ex. 8B-2 T₀ = 810° C.  80% KNO3h = 0.050 cal/cm²-s-° C.  20% NaNO3 Ex. 8B-3 T₀ = 810° C.  50% KNO3 h =0.050 cal/cm²-s-° C.  50% NaNO3 Ex. 8B-4 T₀ = 810° C.  0% KNO3 h = 0.050cal/cm²-s-° C. 100% NaNO3 Low level, Comparative Ex. 8C-1 T₀ = 810° C.Not chemically thermally h = 0.025 cal/cm²-s-° C. strengthenedstrengthened Ex. 8C-2 T₀ = 810° C.  80% KNO3 h = 0.025 cal/cm²-s-° C. 20% NaNO3 Ex. 8C-3 T₀ = 810° C.  50% KNO3 h = 0.025 cal/cm²-s-° C.  50%NaNO3 Ex. 8C-4 T₀ = 810° C.  0% KNO3 h = 0.025 cal/cm²-s-° C. 100% NaNO3

FIG. 33 shows the measured CT values (measured by SCALP) of Examples8A-2 through 8A-4, Examples 8B-2 through 8B-4 and Examples 8C-2 through8C-4, shown as a function of NaNO₃ concentration in the molten saltbath. FIG. 33 also includes the initial CT values (measured by SCALP) ofeach of the three samples of Comparative Examples 8A-1, 8B-1 and 8C-1,which were later chemically strengthened to provide Examples 8A-2through 8A-4, Examples 8B-2 through 8B-4 and Examples 8C-2 through 8C-4,even though Comparative Examples 8A-1, 8B-1 and 8C-1 were not chemicallystrengthened to show “control” values and conditions.

FIG. 34 shows the change in CT or delta CT in absolute terms and FIG. 35shows the change in CT as a percent, between Comparative Example 8A-1and Examples 8A-2 through 8A-4, between Comparative Example 8B-1 andExamples 8B-2 through 8B-4, and between Comparative Example 8C-1 andExamples 8C-2 through 8C-4. As shown in FIGS. 34 and 35, Examples 8C-2through 8C-4 exhibit the greatest percentage change in CT after beingchemically strengthened. These articles were formed from the low level,thermally strengthened glass article (Comparative Ex. 8C-1). Withoutbeing bound by theory, the thermally glass articles exhibiting thelowest fictive temperature can build up the greatest amount of surfacecompressive stress when subsequently chemically strengthened.

The surface CS and CS at DOL (or knee CS) of Examples 8A-2 through 8A-3,Examples 8B-2 through 8B-3 and Examples 8C-2 through 8C-3 was measuredand plotted in FIG. 36, as a function of NaNO₃ concentration. As shownin FIG. 36, surface CS decreased with higher concentrations of NaNO₃ inthe molten salt bath used during chemical strengthening. FIG. 36 alsoshows the similarly in surface CS values between Examples 8A-2, 8B-2 and8C-2, and between Examples 8A-3, 8B-3 and 8C-3.

FIG. 37 shows the measured DOL values of Examples 8A-2 through 8A-3,Examples 8B-2 through 8B-3 and Examples 8C-2 through 8C-3, plotted as afunction of NaNO₃ concentration.

CT and stored tensile energy values of Examples 8A-2 through 8A-4,Examples 8B-2 through 8B-4 and Examples 8C-2 through 8C-4 are shown inTable 25.

TABLE 25 CT and stored tensile energy values of Examples 8A-2 through8A-4, Examples 8B-2 through 8B-4 and Examples 8C-2 through 8C-4. ExampleCT (MPa) Stored Tensile Energy (J/m²) Ex. 8A-2 97.75 13.46 Ex. 8A-3105.88 17.15 Ex. 8A-4 107.26 16.60 Ex. 8B-2 89.73 12.79 Ex. 8B-3 98.7313.32 Ex. 8B-4 97.97 13.47 Ex. 8C-2 73.63 8.84 Ex. 8C-3 87.12 9.21 Ex.8C-4 87.24 10.68

Examples 8A-2 through 8A-4, Examples 8B-2 through 8B-4 and Examples 8C-2through 8C-4 were fractured in the same manner as described in Example7. The Examples with lower stored tensile energy values exhibitedfracturing with higher aspect ratios and/or fewer pieces. Without beingbound by theory, these Examples may be described as exhibiting lessdicing when fractured.

Examples 8B-5 and 8C-5 included identical glass substrates that werethermally strengthened in the same manner as Comparative Examples 8B-1and 8C-1, but were then chemically strengthened by immersing in a mixedmolten salt bath including 20% NaNO₃ and 80% KNO₃ and having atemperature of 430° C. for 1 hour. FIG. 38 is a bar graph showing (fromleft to right) the measured CT, surface CS, DOL and CS at DOL (or kneestress) of Examples 8B-2 (chemically strengthened at 390° C. for 2hours), 8B-5, 8C-2 (chemically strengthened at 390° C. for 2 hours) and8C-5. These values, along with the stored tensile energy, are shown inTable 26.

TABLE 26 Measures stress-related properties of Examples 8B-2, 8B-5, 8C-2and 8C-5. Stored Tensile Energy Surface DOL CS at DOL Example CT (MPa)(J/m²) CS (MPa) (micrometers) (MPa) Medium Ex. 8B-2 89.73 12.79 690.4113.22 184.63 level, Ex. 8B-5 84.95 8.58 666.92 15.49 188.64 thermallystrengthened Low level, Ex. 8C-2 73.63 677.44 12.75 188.1 thermally Ex.8C-5 75.60 7.36 664.42 15.12 173.14 strengthened

As shown in Table 26, the DOL values for Examples 8B-5 and 8C-5 weregreater than Examples 8B-2 and 8C-2, which were chemically strengthenedusing a lower temperature bath (i.e., 390° C.).

FIG. 39 shows the measured DOL alone for Examples 8B-2 (chemicallystrengthened at 390° C. for 2 hours), 8B-5, 8C-2 (chemicallystrengthened at 390° C. for 2 hours) and 8C-5.

Examples 8B-6 through 8B-8 and 8C-6 through 8C-8 included the same glasssubstrate and were thermally strengthened in the same manner asComparative Examples 8B-1 and 8C-1, but were then chemicallystrengthened by immersing in a mixed molten salt bath including NaNO₃and KNO₃ at varying concentrations and having a temperature of 430° C.for 1 hour (to provide Examples 8B-6 through 8B-8 and 8C-6 through8C-8), as shown in Table 27.

TABLE 27 Thermal strengthening and chemical strengthening conditions forExample 8. Thermal strengthening Molten salt bath conditions (T₀, h)composition Medium level, Ex. 8B-6 T₀ = 810° C. 100% KNO3 thermally h =0.050 cal/cm²-s-° C.  0% NaNO3 strengthened Ex. 8B-7 T₀ = 810° C.  95%KNO3 h = 0.050 cal/cm²-s-° C.  5% NaNO3 Ex. 8B-8 T₀ = 810° C.  90% KNO3h = 0.050 cal/cm²-s-° C.  10% NaNO3 Low level, Ex. 8C-6 T₀ = 810° C.100% KNO3 thermally h = 0.025 cal/cm²-s-° C.  0% NaNO3 strengthened Ex.8C-7 T₀ = 810° C.  95% KNO3 h = 0.025 cal/cm²-s-° C.  5% NaNO3 Ex. 8C-8T₀ = 810° C.  90% KNO3 h = 0.025 cal/cm²-s-° C.  10% NaNO3

The CT, stored tensile energy, surface CS, DOL and CS at DOL of Examples8B-6 through 8B-8 and Examples 8C-6 through 8C-8 were measured and areshown in Table 28. Table 28 also includes the measured values forExample 8B-5 and 8C-5, which were chemically strengthened in a 80% KNO₃and 20% NaNO₃ bath having a temperature of 430° C. for 1 hour forcomparison.

TABLE 28 Measures stress-related properties of Examples 8B-5 through8B-9 and Examples 8C-5 through 8C-9. Stored CS Tensile Surface at CTEnergy CS DOL DOL Example (MPa) (J/m²) (MPa) (micrometers) (MPa) MediumEx. 8B-5 84.95 8.48 667 15.5 189 level, Ex. 8B-6 59.70 5.87 948 19.5 106thermally Ex. 8B-7 68.06 7.48 829 16 130 strengthened Ex. 8B-8 76.128.51 762 16 50 Low level, Ex. 8C-5 75.6 7.35 664 15 173 thermally Ex.8C-6 55.53 4.21 945 19.5 108 strengthened Ex. 8C-7 62.62 6.63 831 15 94Ex. 8C-8 69.87 6.98 751 16 100

FIG. 40 plots the CT and surface CS of Examples 8B-5 through 8B-8 andExamples 8C-5 through 8C-8, as a function of NaNO₃ concentration. FIG.41 plots the surface CS as a function of CT. As shown in FIGS. 40 and41, surface CS is reduced when a molten salt bath with higher NaNO₃concentration is used, while CT increases.

The stress profiles for Examples 8C-7 and 8C-9 were measured using aRNF. FIG. 42 shows the measured stress as a function of depth extendingfrom the surface of the thermally and chemically strengthened glassarticles of Examples 8C-7 and 8C-8 into the glass article. The stressprofile of a known glass article that was only chemically strengthenedby immersing in a mixed molten salt bath of 51% KNO₃ and 49% NaNO₃,having a temperature of 380° C. for 3 hours and 45 minutes (ComparativeExample 8D) is also shown in FIG. 42.

Example 9

Substrates made of Glaverbel SLG, having a nominal composition of 70.9mol % SiO₂, 0.8 mol % Al₂O₃, 13.2 mol % Na₂O, 0.11 mol % K₂O, 6.6 mol %MgO, 8.2 mol % CaO, 0.03 Fe₂O₃ and 0.22 mol % SO₃, and having athickness of about 0.73 mm, were thermally strengthened, chemicallystrengthened without prior thermal strengthening, or thermally and thenchemically strengthened.

Specifically, Comparative Example 9A included a thermally strengthenedglass article that was heated to a T₀ of about 690° C. and then quenchedat h=0.051 cal/cm²-s-° C., no chemical strengthening was performed.Comparative Example 9B was a glass substrate that was not thermallystrengthened, but that was chemically strengthened by immersing in amolten salt bath of 100% KNO₃ having a temperature of 420° C. for 5.5hours. Example 9C was a glass substrate that was thermally strengthenedin the same manner as Example 9A, but was then chemically strengthenedby ion-exchange by immersing in a molten salt bath of 100% KNO₃ having atemperature of 420° C. for 5.5 hours, i.e., the same conditions as inComparative Example 9B. See Table 29.

TABLE 29 Thermal strengthening and chemical strengthening conditions forComparative Examples 9A and 9B, and Example 9C. Thermal strengtheningChemical conditions (T₀, h) strengthening Comparative Ex. 9A T₀ = 690°C. None h = 0.051 cal/cm²-s-° C. Comparative Ex. 9B None 100% KNO3, 420°C., 5.5 hours Ex. 9C T₀ = 690° C. 100% KNO3, 420° C., h = 0.051cal/cm²-s-° C. 5.5 hours

The CS, CT, DOL and DOC values (as an absolute measurement and as apercentage of the glass article thickness) of all the resulting glassarticles were measured and are shown in Table 30. As shown in Table 30,Example 9C exhibited a DOL of about 10 micrometers and a surface CS ofabout 600 MPa. By selecting appropriate thermal and chemicalstrengthening conditions, the thermally and chemically strengthenedglass articles of Example 9C exhibit slightly less surface CS values asExample 9B (536 MPa versus 604 MPa), slightly better DOL values (11.7microns versus 10 microns), but a total DOC that is many times largerthan achievable by a chemical strengthening process alone (144 micronsversus 10 microns). That is, thermally conditioned samples that are thensubject to the same IOX conditions as samples that did not have a priorthermal treatment, have an increased DOL. Additionally, by selectingappropriate thermal and chemical strengthening conditions, the thermallyand chemically strengthened glass articles of Example 9C exhibit asimilar DOC as the thermally-only strengthened articles of ComparativeExample 9A (144 microns versus 154 microns), but a much higher surfaceCS than those of Comparative Example 9A (i.e., 536 MPa versus 100 MPa).

TABLE 30 Measured properties of the resulting thermally and chemicallystrengthened glass articles of Comparative Examples 9A and 9B, andExample 9C. CS CT DOL DOC DOC as % of article Example (MPa) (MPa) (inμm) (in μm) thickness Comparative 100 49 0 154 21.1 Ex. 9A Comparative604 9 10 10 1.4 Ex. 9B Ex. 9C 536 21 11.7 144 19.7

The glass substrates of Comparative Examples 9A, 9B, and of Example 9Cwere compared in terms of mechanical performance. Specifically, samplesof these glass substrates or articles were subjected to a Vicker'sindentation threshold test and a Knoop scratch threshold test, asdescribed above in Example 2. The results of each test are shown inTable 31. As is seen from Table 31, the use of thermal and chemicalstrengthening leads to an improvement in the Vickers indentationthreshold over that of only-chemically strengthened substrates. Asfurther seen from Table 31, the use of thermal and chemicalstrengthening also leads to an improvement in the Knoop scratchthreshold over that of only-thermally strengthened substrates; Knoopvalues for Example 9C are lower than those in Comparative Example 9A,and are similar to those achieved in Comparative Example 9B. Also, it isseen that the Comparative Examples 9A had sustained surface cracking(i.e., failure mode 1), whereas Comparative Example 9B and Examples 9Chad surface cracks and/or a median crack (mode 3). Thus, the combinationof thermally and chemically strengthening leads to glass substrateshaving advantaged properties over those having been subject to onlythermal or only chemical strengthening.

TABLE 31 Mechanical performance of the substrates in ComparativeExamples 9A and 9B, and in Example 9C. Failure Vicker's (N) Knoop (N)Mode Comparative Example 9A 4-6 6-8 1 (thermally strengthened only at T₀= 690° C., h = 0.051) Comparative Example 9B 0-2 2-4 3 (chemicallystrengthened only, at 420° C. for 5.5 hours) Example 9C 2-4 2-4 3(thermally strengthened at T₀ = 690° C., h = 0.051, and chemicallystrengthened at 420° C. for 5.5 hours)

Glass substrates prepared as in Comparative Examples 9A and 9B, andExample 9C, were subject to incremental drop testing as set forth inExample 2, above, except that only 180 grit sandpaper drop surface wasused, and were also subject to a four-point bend test (to test edgestrength), again as set forth in Example 2. The results of the droptesting are shown in FIG. 43, whereas results of the four-point bendtest are shown in FIG. 44. From FIG. 43, it is seen that the articles ofExample 9C (which retain much of the DOC as Comparative Example 9A) showdrop performance which is much better than that of Comparative Examples9B, albeit not quite as high as the highest values from ComparativeExamples 9A. From FIG. 44, it is seen that the articles of Example 9Chave a better edge strength despite having a lower surface CS than thoseof Comparative Example 9B; they also have a better edge strength thanthe samples of Comparative Example 9A.

Further, glass substrates prepared as in Comparative Examples 9A and 9B,and Example 9C, were also subject to ring-on-ring testing to testsurface strength. Ring-on-ring testing was carried out as explainedbelow for abraded ring-on-ring (AROR) testing, except that the sampleswere not abraded prior to testing. The results of the ring-on-ringtesting are shown in FIG. 45. As seen from FIG. 45, as expected, thesamples of Comparative Example 9B (having the highest surface CS)performed the best. However, the samples of Example 9C, having aslightly lower surface CS than those of Example 9B, had a better surfacestrength than those of Comparative Example 9A, and slightly lowersurface strength than that of the samples of Comparative Example 9B.

In order to test surface strength of already damaged (as by scratching)glass samples, i.e., retained strength after damage, an abradedring-on-ring test (AROR) was used; this test may be more reflective ofhow the glass samples will perform during real-world use conditions. Thestrength of a material is the stress at which fracture occurs, and theAROR test is a surface strength measurement for testing flat glassspecimens, and ASTM C1499-09 (2013), entitled “Standard Test Method forMonotonic Equibiaxial Flexural Strength of Advanced Ceramics at AmbientTemperature,” serves as the basis for the AROR test methodologydescribed herein. The contents of ASTM C1499-09 are incorporated hereinby reference in their entirety. The glass specimen is abraded prior toring-on-ring testing with 90 grit silicon carbide (SiC) particles thatare delivered to the glass sample using the method and apparatusdescribed in Annex A2, entitled “abrasion Procedures,” of ASTM C158-02(2012), entitled “Standard Test Methods for Strength of Glass by Flexure(Determination of Modulus of Rupture). The contents of ASTM C158-02 andthe contents of Annex 2 in particular are incorporated herein byreference in their entirety.

Prior to ring-on-ring testing a spot on the surface of the glass-basedarticle is abraded as described in ASTM C158-02, Annex 2, to normalizeand/or control the surface defect condition of the sample using theapparatus shown in Figure A2.1 of ASTM C158-02. To form an abraded spot,the abrasive material is sandblasted onto the surface 410 a of theglass-based article at a defined load (herein various loads were used asshown in FIG. 47, e.g., 5, 15, 30, and 45, psi) using an air pressure of304 kPa (44 psi). After air flow is established, 5 cm³ of abrasivematerial is dumped into a funnel and the sample is sandblasted for 5seconds after introduction of the abrasive material. The abraded spotwas about 1 cm in diameter and was located in the center of the sample.During testing, the abraded spot is located concentrically with therings.

For the AROR test, a glass-based article having an abraded spot onsurface 410 a as shown in FIG. 10 is placed between two concentric ringsof differing size to determine equibiaxial flexural strength (i.e., themaximum stress that a material is capable of sustaining when subjectedto flexure between two concentric rings). In the AROR configuration 400,the abraded glass-based article 410 is supported by a support ring 420having a diameter D2. A force F is applied by a load cell (not shown) tothe surface of the glass-based article by a loading ring 430 having adiameter D1.

The ratio of diameters of the loading ring and support ring D1/D2 may bein a range from 0.2 to 0.5. In some embodiments, D1/D2 is 0.5. Loadingand support rings 130, 120 should be aligned concentrically to within0.5% of support ring diameter D2. The load cell used for testing shouldbe accurate to within ±1% at any load within a selected range. Testingis carried out at a temperature of 23±2° C. and a relative humidity of40±10%.

For fixture design, the radius r of the protruding surface of theloading ring 430 is in a range of h/2≤r≤3 h/2, where h is the thicknessof glass-based article 410. Loading and support rings 430, 420 are madeof hardened steel with hardness HRc>40. AROR fixtures are commerciallyavailable.

The intended failure mechanism for the AROR test is to observe fractureof the glass-based article 410 originating from the surface 430 a withinthe loading ring 430. Failures that occur outside of this region—i.e.,between the loading ring 430 and support ring 420—are omitted from dataanalysis. Due to the thinness and high strength of the glass-basedarticle 410, however, large deflections that exceed ½ of the specimenthickness h are sometimes observed. It is therefore not uncommon toobserve a high percentage of failures originating from underneath theloading ring 430. Stress cannot be accurately calculated withoutknowledge of stress development both inside and under the ring(collected via strain gauge analysis) and the origin of failure in eachspecimen. AROR testing therefore focuses on peak load at failure as themeasured response.

The strength of glass-based article depends on the presence of surfaceflaws. However, the likelihood of a flaw of a given size being presentcannot be precisely predicted, as the strength of glass is statisticalin nature. A probability distribution can therefore be used as astatistical representation of the data obtained.

The results of the abraded ring-on-ring test are shown in FIG. 47. Asseen from FIG. 47, the substrates of Example 9C had a better retainedstrength than did the samples of Comparative Example 9B, likely due totheir deeper DOC, albeit not as high as the retained strength of thesamples of Comparative Example 9A. And this was true over a range offlaw sizes as evidenced by the differing pressure used for the abrasiveparticles.

In summary for Example 9, it was possible to use thermally andchemically strengthening together, in a soda-lime glass to produce acombination profile that had a higher DOL and DOC but slightly lower CS.The combination profile showed, as compared to the profile achieved bychemically strengthening alone: deeper DOL and DOC; lower surface CS,but such will not always be the case, depending on the temper level andIOX conditions for the tempered glass; better drop performance (on 180grit sandpaper drop surface); improved edge strength (as by four-pointbend); comparable warp (as by Flatmaster); lower surface strength (as byring-on-ring), but again this will not always be true depending on thelevel of surface CS that can be attained in the combination profile;better retained strength (as by abraded ring-on-ring); improved Vickersindentation threshold; and comparable Knoop scratch performance.

Example 10

Substrates made of Glaverbel SLG, having a nominal composition of 70.9mol % SiO₂, 0.8 mol % Al₂O₃, 13.2 mol % Na₂O, 0.11 mol % K₂O, 6.6 mol %MgO, 8.2 mol % CaO, 0.03 Fe₂O₃ and 0.22 mol % SO₃, and having athickness of about 1.08 mm, were thermally strengthened, chemicallystrengthened without prior thermal strengthening, or thermally and thenchemically strengthened.

Specifically, Comparative Example 10A included a thermally strengthenedglass article that was heated to a T₀ of about 690° C. and then quenchedat h=0.035 cal/cm²-s-° C., no chemical strengthening was performed.Comparative Example 10B was a glass substrate that was not thermallystrengthened, but that was chemically strengthened by immersing in amolten salt bath of 100% KNO₃ having a temperature of 420° C. for 5.5hours. Example 10C was a glass substrate that was thermally strengthenedin the same manner as Example 10A, but was then chemically strengthenedby ion-exchange by immersing in a molten salt bath of 100% KNO₃ having atemperature of 420° C. for 5.5 hours, i.e., the same conditions as inComparative Example 10B. See Table 32.

TABLE 32 Thermal strengthening and chemical strengthening conditions forComparative Examples 10A and 10B, and Example 10C. Thermal strengtheningChemical conditions (T₀, h) strengthening Comparative Ex. 9A T₀ = 690°C. None h = 0.035 cal/cm²-s-° C. Comparative Ex. 9B None 100% KNO3, 420°C., 5.5 hours Ex. 9C T₀ = 690° C. 100% KNO3, 420° C., h = 0.035cal/cm²-s-° C. 5.5 hours

The CS, CT, DOL and DOC values (as an absolute measurement and as apercentage of the glass article thickness) of all the resulting glassarticles were measured and are shown in Table 33. As shown in Table 33,Example 10C exhibited a DOL of about 11 micrometers and a surface CS ofabout 525 MPa. By selecting appropriate thermal and chemicalstrengthening conditions, the thermally and chemically strengthenedglass articles of Example 10C exhibit slightly less surface CS values asExample 10B (525 MPa versus 550 MPa), about the same DOL values (10.9microns versus 10.6 microns), but a total DOC that is many times largerthan achievable by a chemical strengthening process alone (217 micronsversus about 11 microns). Additionally, by selecting appropriate thermaland chemical strengthening conditions, the thermally and chemicallystrengthened glass articles of Example 10C exhibit a similar DOC as thethermally-only strengthened articles of Comparative Example 10A (217microns versus 230 microns), but a much higher surface CS than those ofComparative Example 10A (i.e., 525 MPa versus 118 MPa).

TABLE 33 Measured properties of the resulting thermally and chemicallystrengthened glass articles of Comparative Examples 10A and 10B, andExample 10C. CS CT DOL DOC DOC as % of article Example (MPa) (MPa) (inμm) (in μm) thickness Comparative 118 62 0 230 21.3 Ex. 10A Comparative550 5.5 10.6 10.6 1 Ex. 10B Ex. 10C 525 22.4 10.9 217 20.1

The glass substrates of Comparative Examples 10A, 10B, and of Example10C were compared in terms of mechanical performance. Specifically,samples of these glass substrates or articles were subjected to aVicker's indentation threshold test and a Knoop scratch threshold test,as described above in Example 2. The results of each test are shown inTable 34. As is seen from Table 34, the use of thermal and chemicalstrengthening leads to an improvement in the Vickers indentationthreshold over that of only-chemically strengthened substrates. Asfurther seen from Table 34, the use of thermal and chemicalstrengthening also leads to an improvement in the Knoop scratchthreshold over that of only-thermally strengthened substrates; Knoopvalues for Example 10C are lower than those in Comparative Example 10A,and are similar to those achieved in Comparative Example 10B. Also, itis seen that the Comparative Examples 10A had sustained surface cracking(i.e., failure mode 1), whereas Comparative Example 10B and Examples 10Csimilarly had surface cracks and/or a median crack (mode 3). Thus, thecombination of thermally and chemically strengthening leads to glasssubstrates having advantaged properties over those having been subjectto only thermal or only chemical strengthening. Another thing that canbe seen from Table 34 is that the values for the Vicker's and Knooptests were very similar when performed on the tin side of the substrateand on the air side of the substrate (the tin side being that in contactwith a tin bath during forming of the glass substrate as in a “float”process, the air side being the non-tin side).

TABLE 34 Mechanical performance of the substrates in ComparativeExamples 10A and 10B, and in Example 10C. Failure Vicker's (kg) Knoop(N) Mode Comparative Example 10A 0.6-0.8 (air) 4-6 (air) 1 (thermallystrengthened only at 0.6-0.8 (tin) 4-6 (tin) T₀ = 690° C., h = 0.035)Comparative Example 10B   0-0.2 (air) 2-4 (air) 3 (chemicallystrengthened only,   0-0.2 (tin) 2-4 (tin) at 420° C. for 5.5 hours)Example 10C 0.2-0.4 (air) 2-4 (air) 3 (thermally strengthened at 0 to0.2 (tin) 2-4 (tin) T₀ = 690° C., h = 0.035, and chemically strengthenedat 420° C. for 5.5 hours)

Glass substrates prepared as in Comparative Examples 10A and 10B, andExample 10C, were subject to incremental drop testing as set forth inExample 2, above, except that only 180 grit sandpaper drop surface wasused, and were also subject to a four-point bend test (to test edgestrength), again as set forth in Example 2. The results of the droptesting are shown in FIG. 48, whereas results of the four-point bendtest are shown in FIG. 49. From FIG. 48, it is seen that the articles ofExample 10C (which retain much of the DOC as Comparative Example 10A)show drop performance which is similar to, but slightly better than,that of Comparative Examples 10B, albeit not as high as the values fromComparative Examples 10A. From FIG. 49, it is seen that the articles ofExample 10C have a similar edge strength despite having a lower surfaceCS than those of Comparative Example 10B.

Further, glass substrates prepared as in Comparative Examples 10A and10B, and Example 10C, were also subject to ring-on-ring testing to testsurface strength. Ring-on-ring testing was carried out as explainedabove in connection with Example 9. The results of the ring-on-ringtesting are shown in FIG. 50. As seen from FIG. 50, as expected, thesamples of Comparative Example 10B (having the highest surface CS)performed the best. However, the samples of Example 10C, having aslightly lower surface CS than those of Example 9B, but higher thanthose of Comparative Example 10A, had an unexpectedly lower surfacestrength than those of Comparative Example 9A. It is believed that theparts of Example 10C were scratched in handling which affected theirperformance in this test.

In order to test surface strength of already damaged (as by scratching)glass samples, i.e., retained strength after damage, an abradedring-on-ring test (AROR) was used; this test may be more reflective ofhow the glass samples will perform during real-world use conditions. Theresults of the abraded ring-on-ring test are shown in FIG. 50. As seenfrom FIG. 50, the substrates of Example 10C had a better retainedstrength than did the samples of Comparative Example 10B, likely due totheir deeper DOC, albeit not as high as the retained strength of thesamples of Comparative Example 10A. And this was true over a range offlaw sizes as evidenced by the differing pressure used for the abrasiveparticles.

In summary for Example 10, it was possible to use thermal and chemicalstrengthening together, in a soda-lime glass to produce a combinationprofile that had a higher DOL and DOC but slightly lower CS. Thecombination profile showed, as compared to the profile achieved bychemically strengthening alone: deeper DOL and DOC; lower surface CS,but such will not always be the case, depending on the temper level andIOX conditions for the tempered glass; slightly better drop performance(on 180 grit sandpaper drop surface); similar edge strength (as byfour-point bend); comparable warp; lower surface strength (as byring-on-ring), but again this will not always be true depending on thelevel of surface CS that can be attained in the combination profile;comparable Vickers indentation threshold; and comparable Knoop scratchperformance.

Example 11

The object of this Example 11 was to see whether thermal and chemicaltempering could be used to create a predetermined a thermally achievedsurface CS (from about 70 to about 100 MPa), a thermally achieved CT(from about 35 to about 50 MPa), chemically achieved surface CS of about800 MPa or higher, and DOL (about 12 microns or more) in a particularglass composition. The glass composition was Corning Code 2320(available from Corning Incorporated, Corning, N.Y.), having a nominalcomposition of 61.9 wt % SiO₂, 3.9 wt % B₂O₃, 19.7 wt % Al₂O₃, 12.9 wt %Na₂O, 1.4 wt % MgO, and 0.22 wt % SO₃, and having a thickness of about0.7 mm. Further, the glass samples had a Young's modulus of 70 GPa, alow-temperature CTE of about 75.8×10⁻⁷ (wherein low-temperature CTS isover the range of about 20 to about 300° C.), a softening point of 900°C., and a strain point of about 580° C. Samples of the glass werethermally strengthened, and then chemically strengthened using variousdifferent chemical strengthening conditions.

At first, samples of the glass were thermally treated from a T₀ of 800°C., 810° C., 820° C., 830° C., and 840° C., with h=0.05 cal/cm²-s-° C.These samples were measured with SCALP to obtain the CT and DOC. The CTvalues are shown as a function of temperature in FIG. 52. From FIG. 52it is seen that with the selected h, any T₀ of 810° C. or more shouldachieve a CT of about 35 MPa or more. The DOC was found to be relativelyinvariant and had an average of 152 microns.

From the above initial experiment, a T₀ of 830° C. and h=0.05cal/cm²-s-° C. were chosen for further exploration. Thus, using a T₀ of830° C. and h=0.05 cal/cm²-s-° C., samples were thermally strengthened,and were then further subject to chemical strengthening (by ion-exchangeby immersing in a molten salt bath of 100% KNO₃) at temperatures between390° C. and 430° C. for times ranging from 15 minutes to 1 hour. FSM wasused to characterize the CS and the DOL. The samples were also measuredby SCALP to obtain the CT and DOC after chemical strengthening. Thechemical strengthening conditions, CS, CT, DOL, DOC, and DOC as apercent of thickness are shown in Table 35.

Specifically, Comparative Example 11A included a thermally strengthenedglass article that was heated to a T₀ of about 830° C. and then quenchedat h=0.05 cal/cm²-s-° C. Examples 11B-1 through 11B-3, 11C-1 through11C-3, 11D-1 through 11D-3, 11E-1 through 11E-3, 11F-1 through 11F-3,included glass articles that included the same glass substrate and thatwere thermally strengthened in the same manner as Comparative Examples11A, but were then chemically strengthened by ion-exchange by immersingin a molten salt bath of 100% KNO₃ having a temperature of about 390°C., of about 400° C., of about 410° C., of about 420° C., and about 430°C., for 15 minutes, 30 minutes, and 60 minutes, according to Table 35.

TABLE 35 Thermal strengthening and chemical strengthening conditions forExample 11. Chemical strengthening Thermal strengthening duration andconditions (T₀, h) temperature Comp. Ex. 11A T₀ = 830° C. None h = 0.05cal/cm²-s-° C. Ex. 11B-1 T₀ = 830° C. 15 minutes h = 0.05 cal/cm²-s-° C.390° C. Ex. 11B-2 T₀ = 830° C. 30 minutes h = 0.05 cal/cm²-s-° C. 390°C. Ex. 11B-3 T₀ = 830° C. 60 minutes h = 0.05 cal/cm²-s-° C. 390° C. Ex.11C-1 T₀ = 830° C. 15 minutes h = 0.05 cal/cm²-s-° C. 400° C. Ex. 11C-2T₀ = 830° C. 30 minutes h = 0.05 cal/cm²-s-° C. 400° C. Ex. 11C-3 T₀ =830° C. 60 minutes h = 0.05 cal/cm²-s-° C. 400° C. Ex. 11D-1 T₀ = 830°C. 15 minutes h = 0.05 cal/cm²-s-° C. 410° C. Ex. 11D-2 T₀ = 830° C. 30minutes h = 0.05 cal/cm²-s-° C. 410° C. Ex. 11D-3 T₀ = 830° C. 60minutes h = 0.05 cal/cm²-s-° C. 410° C. Ex. 11E-1 T₀ = 830° C. 15minutes h = 0.05 cal/cm²-s-° C. 420° C. Ex. 11E-2 T₀ = 830° C. 30minutes h = 0.05 cal/cm²-s-° C. 420° C. Ex. 11E-3 T₀ = 830° C. 60minutes h = 0.05 cal/cm²-s-° C. 420° C. Ex. 11F-1 T₀ = 830° C. 15minutes h = 0.05 cal/cm²-s-° C. 430° C. Ex. 11F-2 T₀ = 830° C. 30minutes h = 0.05 cal/cm²-s-° C. 430° C. Ex. 11F-3 T₀ = 830° C. 60minutes h = 0.05 cal/cm²-s-° C. 430° C.

The CS, CT, DOL and DOC values (as an absolute measurement and DOC as apercentage of the glass article thickness) of all the resulting glassarticles were measured and are shown in Table 36. As shown in FIG. 53,showing average CS as a function of IOX time, it is seen that ation-exchange bath temperatures less than about 420° C., the CS isrelatively constant at about 870 MPa in the time range of from about 15minutes to about 60 minutes. As shown in FIG. 54, showing DOL as afunction of IOX time, at times of 15 minutes and greater, a DOL of 12microns or greater can be achieved with bath temperatures ranging fromabout 410° C. to about 430° C., and at times of about 30 minutes andgreater, a DOL of 12 microns or greater can be achieved with bathtemperatures ranging from about 390° C. and greater, for example fromabout 390° C. to about 430° C. In all cases shown in FIG. 54, the CS wasgreater than 800 MPa.

TABLE 36 Measured properties of the resulting thermally and chemicallystrengthened glass articles of Comparative Example 11A, Examples 11B-1through 11B-3, Examples 11C-1 through 11C-3, Examples 11D-1 through11D-3, Examples 11E-1 through 11E-3, Examples 11F-1 through 11F-3. DOCas % DOL DOC of article Example CS (MPa) CT (MPa) (in μm) (in μm)thickness Comp. Ex. 11A 90 44 — 152 21.7 Ex. 11B-1 874 51 8.9 137 19.6Ex. 11B-2 874 54 11.7 122 17.4 Ex. 11B-3 869 56 16.7 120 17.1 Ex. 11C-1874 52 9.2 130 18.6 Ex. 11C-2 881 54 12.7 119 17.0 Ex. 11C-3 876 56 17.1110 15.7 Ex. 11D-1 878 50 11.9 137 19.6 Ex. 11D-2 869 53 15.2 124 17.7Ex. 11D-3 855 58 20.2 111 15.9 Ex. 11E-1 875 50 12.0 129 18.4 Ex. 11E-2855 53 16.3 121 17.3 Ex. 11E-3 829 60 21.6 106 15.1 Ex. 11F-1 860 4812.9 130 18.6 Ex. 11F-2 833 52 17.5 122 17.4 Ex. 11F-3 822 58 24.2 11015.7

Accordingly, with Corning code 2320 glass, the target profile (athermally achieved surface CS from about 70 to about 100 MPa, athermally achieved CT from about 35 to about 50 MPa, chemically achievedsurface CS of about 800 MPa or higher, and DOL of about 12 microns ormore) can be achieved using thermal strengthening conditions of T₀greater than or equal to 830° C., and h of about 0.05 cal/cm²-s-° C.These thermal strengthening conditions will not significantly change thechemical strengthening behavior because the fictive temperature isrelatively constant for all conditions. The subsequent chemicalstrengthening conditions (in a molten salt bath of 100% KNO₃) can be atemperature of 390° C. for greater than 30 minutes, a temperature of400° C. for greater than or equal to 30 minutes, a temperature of 410°C. for greater than or equal to 30 minutes, a temperature of 420° C. forgreater than or equal to 15 minutes, or a temperature of 430° C. forgreater than or equal to 15 minutes. The fictive temperature of theresultant glass will be relatively high, e.g. about 775° C., or about150° C. above the glass transition temperature. The use of thermalstrengthening prior to chemical strengthening (as exemplified by theconditions noted above for this Example 11) is expected to translateinto further improved scratch performance compared with chemicalstrengthening alone.

The strengthened articles disclosed herein may be incorporated intoanother article such as an article with a display (or display articles)(e.g., consumer electronics, including mobile phones, tablets,computers, navigation systems, and the like), architectural articles,transportation articles (e.g., automotive, trains, aircraft, sea craft,etc.), appliance articles, or any article that requires sometransparency, scratch-resistance, abrasion resistance or a combinationthereof. An exemplary article incorporating any of the strengthenedarticles disclosed herein is shown in FIGS. 55A and 55B. Specifically,FIGS. 55A and 55B show a consumer electronic device 5100 including ahousing 5102 having front 5104, back 5106, and side surfaces 5108;electrical components (not shown) that are at least partially inside orentirely within the housing and including at least a controller, amemory, and a display 5110 at or adjacent to the front surface of thehousing; and a cover substrate 5112 at or over the front surface of thehousing such that it is over the display. In some embodiments, the coversubstrate 5112 may include any of the strengthened articles disclosedherein.

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the disclosure. Also, the various features andcharacteristics of the disclosure may be combined in any and allcombinations as exemplified by the following embodiments.

Embodiment 1

A glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t);

a first compressive stress (CS) region comprising a concentration of ametal oxide that is both non-zero and varies along a portion of thethickness; and

a second CS region being substantially free of the metal oxide of thefirst CS region, the second CS region extending from the first CS regionto a depth of compression (DOC) of about 0.17●t or greater, as measuredfrom the first surface.

Embodiment 2

The glass-based article of embodiment 1, wherein the metal oxidecomprises any one of Na₂O, K₂O, Rb₂O and Cs₂O.

Embodiment 3

The glass-based article of embodiment 2, wherein the metal oxidecomprises K₂O.

Embodiment 4

The glass-based article of embodiment 2, wherein the metal oxidecomprises Na₂O.

Embodiment 5

The glass-based article of any one of embodiments 1-4, furthercomprising a central tension (CT) region, wherein the second CS regionand at least a portion of the CT region comprise an identical glasscomposition.

Embodiment 6

The glass-based article of any one of embodiments 1-5, wherein theconcentration of the metal oxide is both non-zero and varies along theportion of the thickness from the first surface to a depth in the rangefrom greater than about 0●t to less than about 0.17●t.

Embodiment 7

The glass-based article of any one of embodiments 1-6, wherein theconcentration of the metal oxide is both non-zero and varies along theportion of the thickness from the first surface to a depth in the rangefrom greater than about 0.01●t to about 0.1●t.

Embodiment 8

The glass-based article of any one of embodiments 1-7, wherein thethickness t is less than about 2 mm.

Embodiment 9

The glass-based article of embodiment 8, wherein the thickness t is lessthan about 1.2 mm.

Embodiment 10

The glass-based article of any one of embodiments 1-9, furthercomprising a surface CS of about 400 MPa or greater.

Embodiment 11

The glass-based article of embodiment 10, further comprising a surfaceCS of about 600 MPa or greater.

Embodiment 12

The glass-based article of any one of the preceding embodiments, furtherexhibiting a Knoop scratch threshold of about 8 N or greater.

Embodiment 13

The glass-based article of any one of the preceding embodiments, furtherexhibiting a Vicker's crack initiation threshold of about 120 N orgreater.

Embodiment 14

A glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t);

a thermally strengthened region extending from the first surface to aDOC, the thermally strengthened region comprising a chemicallystrengthened region extending from the first surface to a depth of layer(DOL);

wherein the DOC is greater than the DOL and the DOC is greater than orequal to about 0.17t.

Embodiment 15

The glass-based article of embodiment 14, wherein the thickness t isless than about 2 mm.

Embodiment 16

The glass-based article of embodiment 15, wherein the thickness t isless than about 1.2 mm.

Embodiment 17

The glass-based article of any one of embodiments 14-16, furthercomprising a surface CS of about 400 MPa or greater.

Embodiment 18

The glass-based article of embodiment 17, further comprising a maximumCT of about 25 MPa or greater.

Embodiment 19

The glass-based article of embodiment 18, further comprising a surfaceCS of about 1 GPa or greater and a maximum central tension (CT) of about75 MPa or greater.

Embodiment 20

The glass-based article of embodiment 19, wherein the maximum CT isabout 80 MPa or greater.

Embodiment 21

The glass-based article of any one of embodiments 14-20, wherein theglass-based article comprises a composition including any one or more ofP₂O₅, Li₂O, and B₂O₃.

Embodiment 22

The glass-based article of any one of embodiments 14-21, wherein theglass-based article comprises a composition including any two or more ofP₂O₅, Li₂O, and B₂O₃.

Embodiment 23

The glass-based article of any one of embodiments 14-22, wherein theglass-based article comprises a stored tensile energy of about 6 J/m² orgreater.

Embodiment 24

The glass-based article of embodiment 23, wherein the stored tensileenergy is about 10 J/m² or greater.

Embodiment 25

The glass-based article of any one of embodiments 14-24, furthercomprising a CS value at the DOL of about 150 MPa or greater.

Embodiment 26

The glass-based article of any one of embodiments 14-25, wherein the DOLis about 10 micrometers or greater.

Embodiment 27

The glass-based article of any one of embodiments 14-26, furtherexhibiting a Knoop scratch threshold of about 8 N or greater.

Embodiment 28

The glass-based article of any one of embodiments 14-27, furtherexhibiting a Vicker's crack initiation threshold of about 120 N orgreater.

Embodiment 29

A glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t);

a first compressive stress (CS) region comprising a concentration of afirst metal oxide that is both non-zero and varies along a portion ofthe thickness and a second metal oxide; and

a second CS region comprising the second metal oxide and beingsubstantially free of the first metal oxide of the first CS region, thesecond CS region extending from the first CS region to a depth ofcompression (DOC) of about 0.17●t or greater, as measured from the firstsurface.

Embodiment 30

The glass-based article of embodiment 29, wherein the first metal oxidecomprises a first metal ion comprising a first diameter, and the secondmetal oxide comprising a second metal ion comprising a second diameter,wherein the second diameter is less than the first diameter.

Embodiment 31

The glass-based article of embodiment 30, wherein the first metal oxidecomprises K₂O and the second metal oxide comprises Na₂O.

Embodiment 32

The glass-based article of any one of embodiments 29-31, furthercomprising a central tension (CT) region, wherein the second CS regionand at least a portion of the CT region comprise an identical glasscomposition.

Embodiment 33

The glass-based article of any one of embodiments 29-32, wherein theconcentration of the first metal oxide is both non-zero and varies alongthe portion of the thickness from the first surface to a depth in therange from greater than about 0●t to less than about 0.17●t.

Embodiment 34

The glass-based article of any one of embodiments 29-33, wherein theconcentration of the first metal oxide is both non-zero and varies alongthe portion of the thickness from the first surface to a depth in therange from greater than about 0.01●t to about 0.1●t.

Embodiment 35

The glass-based article of any one of embodiments 29-34, wherein thethickness t is less than about 2 mm.

Embodiment 36

The glass-based article of embodiment 35, wherein the thickness t isless than about 1.2 mm.

Embodiment 37

The glass-based article of any one of embodiments 29-36, furthercomprising a surface CS of about 400 MPa or greater.

Embodiment 38

The glass-based article of embodiment 37, further comprising a surfaceCS of about 600 MPa or greater.

Embodiment 39

The glass-based article of any one of embodiments 29-38, furtherexhibiting a Knoop scratch threshold of about 8 N or greater.

Embodiment 40

The glass-based article of any one of embodiments 29-39, furtherexhibiting a Vicker's crack initiation threshold of about 120 N orgreater.

Embodiment 41

A chemically strengthened glass-based article comprising:

a first surface and a second surface opposing the first surface defininga thickness (t); and

a thermally strengthened region,

wherein the first surface is flat to 100 μm total indicator run-out(TIR) along any 50 mm or less profile of the first surface,

wherein the glass-based article comprises a glass having a softeningtemperature, expressed in units of ° C., of T_(soft) and an annealingtemperature, expressed in units of ° C., of T_(anneal), and a surfacefictive temperature measured on the first surface of the glass sheetrepresented by Tfs, when expressed in units of ° C. and anon-dimensional surface fictive temperature parameter θs given by(Tfs−T_(anneal))/(T_(soft)−T_(anneal)), wherein the parameter θs is inthe range of from 0.20 to 0.9.

Embodiment 42

The glass-based article of embodiment 41, wherein the glass-basedarticle comprises a glass sheet having a length, expressed inmillimeters, of l, and a width, expressed in millimeters, of w, whereint is less than l and less than w, and l and w are each at least 10 mm.

Embodiment 43

The glass-based article of embodiment 42, wherein either one or both 1and w are at least 40 mm.

Embodiment 44

The glass-based article of embodiment 41 or 42, wherein the ratio l/tand the ratio w/t each are equal to 10/1 or greater.

Embodiment 45

The glass-based article of any one of embodiments 41-44, wherein thefirst surface has a roughness in the range of from 0.2 to 1.5 nm Ra overan area of 10×10 μm.

Embodiment 46

The glass-based article of any one of embodiments 41-45, wherein t isless than 2 mm.

Embodiment 47

The glass-based article of any one of embodiments 41-46, wherein t isabout 1.2 mm or less.

Embodiment 48

The glass-based article of any one of embodiments 41-47, wherein thesurface fictive temperature measured on the first surface is at least50° C. above a glass transition temperature of the glass.

Embodiment 49

The glass-based article of embodiment 48, wherein the surface fictivetemperature measured on the first surface is at least 75° C. above aglass transition temperature of the glass.

Embodiment 50

The glass-based article of any one of embodiments 41-49, furthercomprising a chemically strengthened region that extends from the firstsurface to a DOL, wherein the thermally strengthened region extends fromthe first surface to a DOC, wherein the DOC is greater than the DOL andthe DOC is greater than or equal to about 0.17t.

Embodiment 51

The glass-based article of any one of embodiments 41-50, furthercomprising a surface CS of about 1 GPa or greater and a maximum CT ofabout 75 MPa or greater.

Embodiment 52

The glass-based article of embodiment 51, wherein the maximum CT isabout 80 MPa or greater.

Embodiment 53

The glass-based article of any one of embodiments 41-52, wherein theglass-based article comprises a composition including P₂O₅.

Embodiment 54

The glass-based article of any one of embodiments 41-53, wherein theglass-based article comprises a composition including Li₂O.

Embodiment 55

The glass-based article of any one of embodiments 41-54, wherein theglass-based article comprises a stored tensile energy of about 6 J/m² orgreater.

Embodiment 56

The glass-based article of embodiment 55, wherein the stored tensileenergy is about 10 J/m² or greater.

Embodiment 57

The glass-based article of any one of embodiments 41-56, furthercomprising a CS value at the DOL of about 150 MPa or greater.

Embodiment 58

The glass-based article of any one of embodiments 41-57, wherein the DOLis about 10 micrometers or greater.

Embodiment 59

The glass-based article of any one of embodiments 41-58, furtherexhibiting a Knoop scratch threshold of about 8 N or greater.

Embodiment 60

The glass-based article of any one of embodiments 41-59, furtherexhibiting a Vicker's crack initiation threshold of about 120 N orgreater.

Embodiment 61

A method for strengthening a glass sheet comprising:

cooling a glass sheet having a transition temperature, from atemperature greater than the transition temperature to a temperatureless than the transition temperature by transferring thermal energy fromthe glass sheet to a heat sink by conduction across a gap that is freeof solid or liquid matter such that more than 20% of the thermal energyleaving the glass sheet crosses the gap and is received by the heat sinkto provide a thermally strengthened glass article; and

chemically strengthening the thermally strengthened glass article.

Embodiment 62

The method of embodiment 61, wherein the thermally strengthened glassarticle is chemically strengthened without removing any portion of thethermally strengthened glass sheet.

Embodiment 63

The method of embodiment 62, wherein the thermally strengthened glassarticle is chemically strengthened without removing 3% or more of thethickness of the thermally strengthened glass sheet.

Embodiment 64

The method of any one of embodiments 61-63, wherein cooling the glasssheet comprises cooling at a rate of about −270° C./second or greater.

Embodiment 65

The method of any one of embodiments 61-64, wherein the thermallystrengthened glass article comprises a thickness and a DOC greater thanor equal to 0.17 times the thickness of the thermally strengthened glassarticle.

Embodiment 66

The method of any one of embodiments 61-65, wherein chemicallystrengthening the thermally strengthened glass sheet comprisesgenerating a surface CS of about 700 MPa or greater, while maintainingthe DOC.

Embodiment 67

The method of embodiment 66, wherein chemically strengthening thethermally strengthened glass article comprises generating a chemicallystrengthened region that extends from a first surface of the glass-basedlayer to a DOL that is greater than or equal to about 10 micrometers.

Embodiment 68

The method of any one of embodiments 61-66, wherein chemicallystrengthening the thermally strengthened glass article comprisesimmersing the thermally strengthened glass sheet in a molten salt bathcomprising any one or more of KNO₃, NaNO₃, and LiNO₃.

Embodiment 69

The method of embodiment 68, wherein the molten salt bath comprises KNO₃and NaNO₃ and has a temperature in the range from about 380° C. to about430° C.

Embodiment 70

A consumer electronic product, comprising:

a housing having a front surface, a back surface and side surfaces;

electrical components provided at least partially internal to thehousing, the electrical components including at least a controller, amemory, and a display, the display being provided at or adjacent thefront surface of the housing; and

a cover article provided at or over the front surface of the housingsuch that it is provided over the display, the cover glass-based articlebeing thermally and chemically strengthened and including first surfaceand a second surface opposing the first surface defining a thickness(t), a first CS region comprising a concentration of a metal oxide thatis both non-zero and varies along a portion of the thickness, and asecond CS region being substantially free of the metal oxide of thefirst CS region, the second CS region extending from the first CS regionto a DOC of about 0.17●t or greater, and

wherein the consumer electronic product is a mobile phone, portablemedia player, notebook computer or tablet computer.

Embodiment 71

A consumer electronic product, comprising:

a housing having a front surface, a back surface and side surfaces;

electrical components provided at least partially internal to thehousing, the electrical components including at least a controller, amemory, and a display, the display being provided at or adjacent thefront surface of the housing; and

a cover article provided at or over the front surface of the housingsuch that it is provided over the display, the cover glass-based articlecomprising the glass-based article of any one of embodiments 1-60.

Embodiment 72

A laminate comprising a first glass-based sheet, a second glass-basedsheet and an interlayer disposed between the first glass-based sheet andthe second glass-based sheet,

wherein either one or both the first and second glass-based sheetcomprises a first surface and a second surface opposing the firstsurface defining a thickness (t), a first CS region comprising aconcentration of a metal oxide that is both non-zero and varies along aportion of the thickness, and a second CS region being substantiallyfree of the metal oxide of the first CS region, the second CS regionextending from the first CS region to a DOC of about 0.17●t or greater.

Embodiment 73

The laminate of embodiment 71, wherein one of the first glass-basedsheet and the second glass-based sheet is cold-formed.

Embodiment 74

A laminate comprising a first glass-based sheet, a second glass-basedsheet and an interlayer disposed between the first glass-based sheet andthe second glass-based sheet,

wherein either one or both the first and second glass-based sheetcomprises the glass-based article of any one of embodiments 1-60.

Embodiment 75

The laminate of embodiment 74, wherein one of the first glass-basedsheet and the second glass-based sheet is cold-formed.

Embodiment 76

A vehicle comprising an opening; and a laminate disposed in the opening,

wherein the laminate comprises a first glass-based sheet, a secondglass-based sheet and an interlayer disposed between the firstglass-based sheet and the second glass-based sheet, and

wherein either one or both the first and second glass-based sheetcomprises a first surface and a second surface opposing the firstsurface defining a thickness (t), a first CS region comprising aconcentration of a metal oxide that is both non-zero and varies along aportion of the thickness, and a second CS region being substantiallyfree of the metal oxide of the first CS region, the second CS regionextending from the first CS region to a DOC of about 0.17●t or greater.

Embodiment 77

The vehicle of embodiment 65, wherein one of the first glass-based sheetand the second glass-based sheet is cold-formed.

Embodiment 78

The vehicle of embodiment 65 or embodiment 66, wherein the firstglass-based sheet is complexly-curved and has at least one concavesurface providing a first surface of the laminate and at least oneconvex surface to provide a second surface of the laminate opposite thefirst surface with a thickness therebetween,

wherein and the second glass-based sheet is complexly-curved and has atleast one concave surface to provide a third surface of the laminate andat least one convex surface to provide a fourth surface of the laminateopposite the third surface with a thickness therebetween; and

wherein the third and fourth surfaces respectively have CS values suchthat the fourth surface has a CS value that is greater than the CS valueof the third surface.

Embodiment 79

The vehicle of embodiment 67, wherein one of the first glass-basedsubstrate or the second glass-based substrate has a thickness in therange of about 0.2 mm to about 0.7 mm.

Embodiment 80

The vehicle of any one of embodiments 67-68, wherein the fourth surfaceof the laminate has a greater CS than the fourth surface has in a flatstate and the laminate is free from optical distortions.

Embodiment 81

The vehicle of embodiment 69, wherein a peripheral portion of the secondglass-based substrate exerts a compressive force against the interlayer,and a center portion of the second glass-based substrate exerts atensile force against the interlayer.

Embodiment 82

The vehicle of embodiment 70, wherein the second glass-based substrateconforms to the first glass-based substrate to provide a substantiallyuniform distance between the convex surface of the second glass-basedsubstrate and the concave surface of the first glass-based substrate,which is filled by the intervening interlayer.

Embodiment 83

A vehicle comprising an opening; and a laminate disposed in the opening,

wherein the laminate comprises a first glass-based sheet, a secondglass-based sheet and an interlayer disposed between the firstglass-based sheet and the second glass-based sheet, and

wherein either one or both the first and second glass-based sheetcomprises the glass-based article of any one of embodiments 1-60.

Embodiment 84

The vehicle of embodiment 83, wherein one of the first glass-based sheetand the second glass-based sheet is cold-formed.

Embodiment 85

The vehicle of embodiment 83 or embodiment 84, wherein the firstglass-based sheet is complexly-curved and has at least one concavesurface providing a first surface of the laminate and at least oneconvex surface to provide a second surface of the laminate opposite thefirst surface with a thickness therebetween,

wherein and the second glass-based sheet is complexly-curved and has atleast one concave surface to provide a third surface of the laminate andat least one convex surface to provide a fourth surface of the laminateopposite the third surface with a thickness therebetween; and

wherein the third and fourth surfaces respectively have CS values suchthat the fourth surface has a CS value that is greater than the CS valueof the third surface.

Embodiment 86

The vehicle of embodiment 85, wherein one of the first glass-basedsubstrate or the second glass-based substrate has a thickness in therange of about 0.2 mm to about 0.7 mm.

Embodiment 87

The vehicle of any one of embodiments 83-86, wherein the fourth surfaceof the laminate has a greater CS than the fourth surface has in a flatstate and the laminate is free from optical distortions.

Embodiment 88

The vehicle of embodiment 87, wherein a peripheral portion of the secondglass-based substrate exerts a compressive force against the interlayer,and a center portion of the second glass-based substrate exerts atensile force against the interlayer.

Embodiment 89

The vehicle of embodiment 88, wherein the second glass-based substrateconforms to the first glass-based substrate to provide a substantiallyuniform distance between the convex surface of the second glass-basedsubstrate and the concave surface of the first glass-based substrate,which is filled by the intervening interlayer.

Embodiment 90

The vehicle of any one of embodiments 83-89, further exhibiting a Knoopscratch threshold of about 8 N or greater, as measured on a surface ofthe glass-based article.

Embodiment 91

The glass-based article of any one of embodiments 83-90, furtherexhibiting a Vicker's crack initiation threshold of about 120 N orgreater, as measured on a surface of the glass-based article.

What is claimed is:
 1. A method for strengthening a glass sheetcomprising: cooling a glass sheet having a transition temperature, froma temperature greater than the transition temperature to a temperatureless than the transition temperature by transferring thermal energy fromthe glass sheet to a heat sink by conduction across a gap that is freeof solid or liquid matter such that more than 20% of the thermal energyleaving the glass sheet crosses the gap and is received by the heat sinkto provide a thermally strengthened glass article; and chemicallystrengthening the thermally strengthened glass article.
 2. The method ofclaim 1, wherein the thermally strengthened glass article is chemicallystrengthened without removing any portion of the thermally strengthenedglass sheet.
 3. The method of claim 2, wherein the thermallystrengthened glass article is chemically strengthened without removing3% or more of the thickness of the thermally strengthened glass sheet.4. The method of claim 1, wherein cooling the glass sheet comprisescooling at a rate of about −270° C./second or greater.
 5. The method ofclaim 1, wherein the thermally strengthened glass article comprises athickness and a DOC greater than or equal to 0.17 times the thickness ofthe thermally strengthened glass article.
 6. The method of claim 1,wherein chemically strengthening the thermally strengthened glass sheetcomprises generating a surface CS of about 700 MPa or greater, whilemaintaining the DOC.
 7. The method of claim 6, wherein chemicallystrengthening the thermally strengthened glass article comprisesgenerating a chemically strengthened region that extends from a firstsurface of the glass-based layer to a DOL that is greater than or equalto about 10 micrometers.
 8. The method of claim 1, wherein chemicallystrengthening the thermally strengthened glass article comprisesimmersing the thermally strengthened glass sheet in a molten salt bathcomprising any one or more of KNO₃, NaNO₃, and LiNO₃.
 9. The method ofclaim 8, wherein the molten salt bath comprises KNO₃ and NaNO₃ and has atemperature in the range from about 380° C. to about 430° C.